refs / files-backend.con commit Merge branch 'xy/format-patch-base' (2cef68f)
   1#include "../cache.h"
   2#include "../refs.h"
   3#include "refs-internal.h"
   4#include "../iterator.h"
   5#include "../dir-iterator.h"
   6#include "../lockfile.h"
   7#include "../object.h"
   8#include "../dir.h"
   9
  10struct ref_lock {
  11        char *ref_name;
  12        struct lock_file *lk;
  13        struct object_id old_oid;
  14};
  15
  16struct ref_entry;
  17
  18/*
  19 * Information used (along with the information in ref_entry) to
  20 * describe a single cached reference.  This data structure only
  21 * occurs embedded in a union in struct ref_entry, and only when
  22 * (ref_entry->flag & REF_DIR) is zero.
  23 */
  24struct ref_value {
  25        /*
  26         * The name of the object to which this reference resolves
  27         * (which may be a tag object).  If REF_ISBROKEN, this is
  28         * null.  If REF_ISSYMREF, then this is the name of the object
  29         * referred to by the last reference in the symlink chain.
  30         */
  31        struct object_id oid;
  32
  33        /*
  34         * If REF_KNOWS_PEELED, then this field holds the peeled value
  35         * of this reference, or null if the reference is known not to
  36         * be peelable.  See the documentation for peel_ref() for an
  37         * exact definition of "peelable".
  38         */
  39        struct object_id peeled;
  40};
  41
  42struct files_ref_store;
  43
  44/*
  45 * Information used (along with the information in ref_entry) to
  46 * describe a level in the hierarchy of references.  This data
  47 * structure only occurs embedded in a union in struct ref_entry, and
  48 * only when (ref_entry.flag & REF_DIR) is set.  In that case,
  49 * (ref_entry.flag & REF_INCOMPLETE) determines whether the references
  50 * in the directory have already been read:
  51 *
  52 *     (ref_entry.flag & REF_INCOMPLETE) unset -- a directory of loose
  53 *         or packed references, already read.
  54 *
  55 *     (ref_entry.flag & REF_INCOMPLETE) set -- a directory of loose
  56 *         references that hasn't been read yet (nor has any of its
  57 *         subdirectories).
  58 *
  59 * Entries within a directory are stored within a growable array of
  60 * pointers to ref_entries (entries, nr, alloc).  Entries 0 <= i <
  61 * sorted are sorted by their component name in strcmp() order and the
  62 * remaining entries are unsorted.
  63 *
  64 * Loose references are read lazily, one directory at a time.  When a
  65 * directory of loose references is read, then all of the references
  66 * in that directory are stored, and REF_INCOMPLETE stubs are created
  67 * for any subdirectories, but the subdirectories themselves are not
  68 * read.  The reading is triggered by get_ref_dir().
  69 */
  70struct ref_dir {
  71        int nr, alloc;
  72
  73        /*
  74         * Entries with index 0 <= i < sorted are sorted by name.  New
  75         * entries are appended to the list unsorted, and are sorted
  76         * only when required; thus we avoid the need to sort the list
  77         * after the addition of every reference.
  78         */
  79        int sorted;
  80
  81        /* A pointer to the files_ref_store that contains this ref_dir. */
  82        struct files_ref_store *ref_store;
  83
  84        struct ref_entry **entries;
  85};
  86
  87/*
  88 * Bit values for ref_entry::flag.  REF_ISSYMREF=0x01,
  89 * REF_ISPACKED=0x02, REF_ISBROKEN=0x04 and REF_BAD_NAME=0x08 are
  90 * public values; see refs.h.
  91 */
  92
  93/*
  94 * The field ref_entry->u.value.peeled of this value entry contains
  95 * the correct peeled value for the reference, which might be
  96 * null_sha1 if the reference is not a tag or if it is broken.
  97 */
  98#define REF_KNOWS_PEELED 0x10
  99
 100/* ref_entry represents a directory of references */
 101#define REF_DIR 0x20
 102
 103/*
 104 * Entry has not yet been read from disk (used only for REF_DIR
 105 * entries representing loose references)
 106 */
 107#define REF_INCOMPLETE 0x40
 108
 109/*
 110 * A ref_entry represents either a reference or a "subdirectory" of
 111 * references.
 112 *
 113 * Each directory in the reference namespace is represented by a
 114 * ref_entry with (flags & REF_DIR) set and containing a subdir member
 115 * that holds the entries in that directory that have been read so
 116 * far.  If (flags & REF_INCOMPLETE) is set, then the directory and
 117 * its subdirectories haven't been read yet.  REF_INCOMPLETE is only
 118 * used for loose reference directories.
 119 *
 120 * References are represented by a ref_entry with (flags & REF_DIR)
 121 * unset and a value member that describes the reference's value.  The
 122 * flag member is at the ref_entry level, but it is also needed to
 123 * interpret the contents of the value field (in other words, a
 124 * ref_value object is not very much use without the enclosing
 125 * ref_entry).
 126 *
 127 * Reference names cannot end with slash and directories' names are
 128 * always stored with a trailing slash (except for the top-level
 129 * directory, which is always denoted by "").  This has two nice
 130 * consequences: (1) when the entries in each subdir are sorted
 131 * lexicographically by name (as they usually are), the references in
 132 * a whole tree can be generated in lexicographic order by traversing
 133 * the tree in left-to-right, depth-first order; (2) the names of
 134 * references and subdirectories cannot conflict, and therefore the
 135 * presence of an empty subdirectory does not block the creation of a
 136 * similarly-named reference.  (The fact that reference names with the
 137 * same leading components can conflict *with each other* is a
 138 * separate issue that is regulated by verify_refname_available().)
 139 *
 140 * Please note that the name field contains the fully-qualified
 141 * reference (or subdirectory) name.  Space could be saved by only
 142 * storing the relative names.  But that would require the full names
 143 * to be generated on the fly when iterating in do_for_each_ref(), and
 144 * would break callback functions, who have always been able to assume
 145 * that the name strings that they are passed will not be freed during
 146 * the iteration.
 147 */
 148struct ref_entry {
 149        unsigned char flag; /* ISSYMREF? ISPACKED? */
 150        union {
 151                struct ref_value value; /* if not (flags&REF_DIR) */
 152                struct ref_dir subdir; /* if (flags&REF_DIR) */
 153        } u;
 154        /*
 155         * The full name of the reference (e.g., "refs/heads/master")
 156         * or the full name of the directory with a trailing slash
 157         * (e.g., "refs/heads/"):
 158         */
 159        char name[FLEX_ARRAY];
 160};
 161
 162static void read_loose_refs(const char *dirname, struct ref_dir *dir);
 163static int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len);
 164static struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
 165                                          const char *dirname, size_t len,
 166                                          int incomplete);
 167static void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry);
 168static int files_log_ref_write(struct files_ref_store *refs,
 169                               const char *refname, const unsigned char *old_sha1,
 170                               const unsigned char *new_sha1, const char *msg,
 171                               int flags, struct strbuf *err);
 172
 173static struct ref_dir *get_ref_dir(struct ref_entry *entry)
 174{
 175        struct ref_dir *dir;
 176        assert(entry->flag & REF_DIR);
 177        dir = &entry->u.subdir;
 178        if (entry->flag & REF_INCOMPLETE) {
 179                read_loose_refs(entry->name, dir);
 180
 181                /*
 182                 * Manually add refs/bisect, which, being
 183                 * per-worktree, might not appear in the directory
 184                 * listing for refs/ in the main repo.
 185                 */
 186                if (!strcmp(entry->name, "refs/")) {
 187                        int pos = search_ref_dir(dir, "refs/bisect/", 12);
 188                        if (pos < 0) {
 189                                struct ref_entry *child_entry;
 190                                child_entry = create_dir_entry(dir->ref_store,
 191                                                               "refs/bisect/",
 192                                                               12, 1);
 193                                add_entry_to_dir(dir, child_entry);
 194                                read_loose_refs("refs/bisect",
 195                                                &child_entry->u.subdir);
 196                        }
 197                }
 198                entry->flag &= ~REF_INCOMPLETE;
 199        }
 200        return dir;
 201}
 202
 203static struct ref_entry *create_ref_entry(const char *refname,
 204                                          const unsigned char *sha1, int flag,
 205                                          int check_name)
 206{
 207        struct ref_entry *ref;
 208
 209        if (check_name &&
 210            check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
 211                die("Reference has invalid format: '%s'", refname);
 212        FLEX_ALLOC_STR(ref, name, refname);
 213        hashcpy(ref->u.value.oid.hash, sha1);
 214        oidclr(&ref->u.value.peeled);
 215        ref->flag = flag;
 216        return ref;
 217}
 218
 219static void clear_ref_dir(struct ref_dir *dir);
 220
 221static void free_ref_entry(struct ref_entry *entry)
 222{
 223        if (entry->flag & REF_DIR) {
 224                /*
 225                 * Do not use get_ref_dir() here, as that might
 226                 * trigger the reading of loose refs.
 227                 */
 228                clear_ref_dir(&entry->u.subdir);
 229        }
 230        free(entry);
 231}
 232
 233/*
 234 * Add a ref_entry to the end of dir (unsorted).  Entry is always
 235 * stored directly in dir; no recursion into subdirectories is
 236 * done.
 237 */
 238static void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry)
 239{
 240        ALLOC_GROW(dir->entries, dir->nr + 1, dir->alloc);
 241        dir->entries[dir->nr++] = entry;
 242        /* optimize for the case that entries are added in order */
 243        if (dir->nr == 1 ||
 244            (dir->nr == dir->sorted + 1 &&
 245             strcmp(dir->entries[dir->nr - 2]->name,
 246                    dir->entries[dir->nr - 1]->name) < 0))
 247                dir->sorted = dir->nr;
 248}
 249
 250/*
 251 * Clear and free all entries in dir, recursively.
 252 */
 253static void clear_ref_dir(struct ref_dir *dir)
 254{
 255        int i;
 256        for (i = 0; i < dir->nr; i++)
 257                free_ref_entry(dir->entries[i]);
 258        free(dir->entries);
 259        dir->sorted = dir->nr = dir->alloc = 0;
 260        dir->entries = NULL;
 261}
 262
 263/*
 264 * Create a struct ref_entry object for the specified dirname.
 265 * dirname is the name of the directory with a trailing slash (e.g.,
 266 * "refs/heads/") or "" for the top-level directory.
 267 */
 268static struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
 269                                          const char *dirname, size_t len,
 270                                          int incomplete)
 271{
 272        struct ref_entry *direntry;
 273        FLEX_ALLOC_MEM(direntry, name, dirname, len);
 274        direntry->u.subdir.ref_store = ref_store;
 275        direntry->flag = REF_DIR | (incomplete ? REF_INCOMPLETE : 0);
 276        return direntry;
 277}
 278
 279static int ref_entry_cmp(const void *a, const void *b)
 280{
 281        struct ref_entry *one = *(struct ref_entry **)a;
 282        struct ref_entry *two = *(struct ref_entry **)b;
 283        return strcmp(one->name, two->name);
 284}
 285
 286static void sort_ref_dir(struct ref_dir *dir);
 287
 288struct string_slice {
 289        size_t len;
 290        const char *str;
 291};
 292
 293static int ref_entry_cmp_sslice(const void *key_, const void *ent_)
 294{
 295        const struct string_slice *key = key_;
 296        const struct ref_entry *ent = *(const struct ref_entry * const *)ent_;
 297        int cmp = strncmp(key->str, ent->name, key->len);
 298        if (cmp)
 299                return cmp;
 300        return '\0' - (unsigned char)ent->name[key->len];
 301}
 302
 303/*
 304 * Return the index of the entry with the given refname from the
 305 * ref_dir (non-recursively), sorting dir if necessary.  Return -1 if
 306 * no such entry is found.  dir must already be complete.
 307 */
 308static int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len)
 309{
 310        struct ref_entry **r;
 311        struct string_slice key;
 312
 313        if (refname == NULL || !dir->nr)
 314                return -1;
 315
 316        sort_ref_dir(dir);
 317        key.len = len;
 318        key.str = refname;
 319        r = bsearch(&key, dir->entries, dir->nr, sizeof(*dir->entries),
 320                    ref_entry_cmp_sslice);
 321
 322        if (r == NULL)
 323                return -1;
 324
 325        return r - dir->entries;
 326}
 327
 328/*
 329 * Search for a directory entry directly within dir (without
 330 * recursing).  Sort dir if necessary.  subdirname must be a directory
 331 * name (i.e., end in '/').  If mkdir is set, then create the
 332 * directory if it is missing; otherwise, return NULL if the desired
 333 * directory cannot be found.  dir must already be complete.
 334 */
 335static struct ref_dir *search_for_subdir(struct ref_dir *dir,
 336                                         const char *subdirname, size_t len,
 337                                         int mkdir)
 338{
 339        int entry_index = search_ref_dir(dir, subdirname, len);
 340        struct ref_entry *entry;
 341        if (entry_index == -1) {
 342                if (!mkdir)
 343                        return NULL;
 344                /*
 345                 * Since dir is complete, the absence of a subdir
 346                 * means that the subdir really doesn't exist;
 347                 * therefore, create an empty record for it but mark
 348                 * the record complete.
 349                 */
 350                entry = create_dir_entry(dir->ref_store, subdirname, len, 0);
 351                add_entry_to_dir(dir, entry);
 352        } else {
 353                entry = dir->entries[entry_index];
 354        }
 355        return get_ref_dir(entry);
 356}
 357
 358/*
 359 * If refname is a reference name, find the ref_dir within the dir
 360 * tree that should hold refname.  If refname is a directory name
 361 * (i.e., ends in '/'), then return that ref_dir itself.  dir must
 362 * represent the top-level directory and must already be complete.
 363 * Sort ref_dirs and recurse into subdirectories as necessary.  If
 364 * mkdir is set, then create any missing directories; otherwise,
 365 * return NULL if the desired directory cannot be found.
 366 */
 367static struct ref_dir *find_containing_dir(struct ref_dir *dir,
 368                                           const char *refname, int mkdir)
 369{
 370        const char *slash;
 371        for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) {
 372                size_t dirnamelen = slash - refname + 1;
 373                struct ref_dir *subdir;
 374                subdir = search_for_subdir(dir, refname, dirnamelen, mkdir);
 375                if (!subdir) {
 376                        dir = NULL;
 377                        break;
 378                }
 379                dir = subdir;
 380        }
 381
 382        return dir;
 383}
 384
 385/*
 386 * Find the value entry with the given name in dir, sorting ref_dirs
 387 * and recursing into subdirectories as necessary.  If the name is not
 388 * found or it corresponds to a directory entry, return NULL.
 389 */
 390static struct ref_entry *find_ref(struct ref_dir *dir, const char *refname)
 391{
 392        int entry_index;
 393        struct ref_entry *entry;
 394        dir = find_containing_dir(dir, refname, 0);
 395        if (!dir)
 396                return NULL;
 397        entry_index = search_ref_dir(dir, refname, strlen(refname));
 398        if (entry_index == -1)
 399                return NULL;
 400        entry = dir->entries[entry_index];
 401        return (entry->flag & REF_DIR) ? NULL : entry;
 402}
 403
 404/*
 405 * Remove the entry with the given name from dir, recursing into
 406 * subdirectories as necessary.  If refname is the name of a directory
 407 * (i.e., ends with '/'), then remove the directory and its contents.
 408 * If the removal was successful, return the number of entries
 409 * remaining in the directory entry that contained the deleted entry.
 410 * If the name was not found, return -1.  Please note that this
 411 * function only deletes the entry from the cache; it does not delete
 412 * it from the filesystem or ensure that other cache entries (which
 413 * might be symbolic references to the removed entry) are updated.
 414 * Nor does it remove any containing dir entries that might be made
 415 * empty by the removal.  dir must represent the top-level directory
 416 * and must already be complete.
 417 */
 418static int remove_entry(struct ref_dir *dir, const char *refname)
 419{
 420        int refname_len = strlen(refname);
 421        int entry_index;
 422        struct ref_entry *entry;
 423        int is_dir = refname[refname_len - 1] == '/';
 424        if (is_dir) {
 425                /*
 426                 * refname represents a reference directory.  Remove
 427                 * the trailing slash; otherwise we will get the
 428                 * directory *representing* refname rather than the
 429                 * one *containing* it.
 430                 */
 431                char *dirname = xmemdupz(refname, refname_len - 1);
 432                dir = find_containing_dir(dir, dirname, 0);
 433                free(dirname);
 434        } else {
 435                dir = find_containing_dir(dir, refname, 0);
 436        }
 437        if (!dir)
 438                return -1;
 439        entry_index = search_ref_dir(dir, refname, refname_len);
 440        if (entry_index == -1)
 441                return -1;
 442        entry = dir->entries[entry_index];
 443
 444        memmove(&dir->entries[entry_index],
 445                &dir->entries[entry_index + 1],
 446                (dir->nr - entry_index - 1) * sizeof(*dir->entries)
 447                );
 448        dir->nr--;
 449        if (dir->sorted > entry_index)
 450                dir->sorted--;
 451        free_ref_entry(entry);
 452        return dir->nr;
 453}
 454
 455/*
 456 * Add a ref_entry to the ref_dir (unsorted), recursing into
 457 * subdirectories as necessary.  dir must represent the top-level
 458 * directory.  Return 0 on success.
 459 */
 460static int add_ref(struct ref_dir *dir, struct ref_entry *ref)
 461{
 462        dir = find_containing_dir(dir, ref->name, 1);
 463        if (!dir)
 464                return -1;
 465        add_entry_to_dir(dir, ref);
 466        return 0;
 467}
 468
 469/*
 470 * Emit a warning and return true iff ref1 and ref2 have the same name
 471 * and the same sha1.  Die if they have the same name but different
 472 * sha1s.
 473 */
 474static int is_dup_ref(const struct ref_entry *ref1, const struct ref_entry *ref2)
 475{
 476        if (strcmp(ref1->name, ref2->name))
 477                return 0;
 478
 479        /* Duplicate name; make sure that they don't conflict: */
 480
 481        if ((ref1->flag & REF_DIR) || (ref2->flag & REF_DIR))
 482                /* This is impossible by construction */
 483                die("Reference directory conflict: %s", ref1->name);
 484
 485        if (oidcmp(&ref1->u.value.oid, &ref2->u.value.oid))
 486                die("Duplicated ref, and SHA1s don't match: %s", ref1->name);
 487
 488        warning("Duplicated ref: %s", ref1->name);
 489        return 1;
 490}
 491
 492/*
 493 * Sort the entries in dir non-recursively (if they are not already
 494 * sorted) and remove any duplicate entries.
 495 */
 496static void sort_ref_dir(struct ref_dir *dir)
 497{
 498        int i, j;
 499        struct ref_entry *last = NULL;
 500
 501        /*
 502         * This check also prevents passing a zero-length array to qsort(),
 503         * which is a problem on some platforms.
 504         */
 505        if (dir->sorted == dir->nr)
 506                return;
 507
 508        QSORT(dir->entries, dir->nr, ref_entry_cmp);
 509
 510        /* Remove any duplicates: */
 511        for (i = 0, j = 0; j < dir->nr; j++) {
 512                struct ref_entry *entry = dir->entries[j];
 513                if (last && is_dup_ref(last, entry))
 514                        free_ref_entry(entry);
 515                else
 516                        last = dir->entries[i++] = entry;
 517        }
 518        dir->sorted = dir->nr = i;
 519}
 520
 521/*
 522 * Return true if refname, which has the specified oid and flags, can
 523 * be resolved to an object in the database. If the referred-to object
 524 * does not exist, emit a warning and return false.
 525 */
 526static int ref_resolves_to_object(const char *refname,
 527                                  const struct object_id *oid,
 528                                  unsigned int flags)
 529{
 530        if (flags & REF_ISBROKEN)
 531                return 0;
 532        if (!has_sha1_file(oid->hash)) {
 533                error("%s does not point to a valid object!", refname);
 534                return 0;
 535        }
 536        return 1;
 537}
 538
 539/*
 540 * Return true if the reference described by entry can be resolved to
 541 * an object in the database; otherwise, emit a warning and return
 542 * false.
 543 */
 544static int entry_resolves_to_object(struct ref_entry *entry)
 545{
 546        return ref_resolves_to_object(entry->name,
 547                                      &entry->u.value.oid, entry->flag);
 548}
 549
 550typedef int each_ref_entry_fn(struct ref_entry *entry, void *cb_data);
 551
 552/*
 553 * Call fn for each reference in dir that has index in the range
 554 * offset <= index < dir->nr.  Recurse into subdirectories that are in
 555 * that index range, sorting them before iterating.  This function
 556 * does not sort dir itself; it should be sorted beforehand.  fn is
 557 * called for all references, including broken ones.
 558 */
 559static int do_for_each_entry_in_dir(struct ref_dir *dir, int offset,
 560                                    each_ref_entry_fn fn, void *cb_data)
 561{
 562        int i;
 563        assert(dir->sorted == dir->nr);
 564        for (i = offset; i < dir->nr; i++) {
 565                struct ref_entry *entry = dir->entries[i];
 566                int retval;
 567                if (entry->flag & REF_DIR) {
 568                        struct ref_dir *subdir = get_ref_dir(entry);
 569                        sort_ref_dir(subdir);
 570                        retval = do_for_each_entry_in_dir(subdir, 0, fn, cb_data);
 571                } else {
 572                        retval = fn(entry, cb_data);
 573                }
 574                if (retval)
 575                        return retval;
 576        }
 577        return 0;
 578}
 579
 580/*
 581 * Load all of the refs from the dir into our in-memory cache. The hard work
 582 * of loading loose refs is done by get_ref_dir(), so we just need to recurse
 583 * through all of the sub-directories. We do not even need to care about
 584 * sorting, as traversal order does not matter to us.
 585 */
 586static void prime_ref_dir(struct ref_dir *dir)
 587{
 588        int i;
 589        for (i = 0; i < dir->nr; i++) {
 590                struct ref_entry *entry = dir->entries[i];
 591                if (entry->flag & REF_DIR)
 592                        prime_ref_dir(get_ref_dir(entry));
 593        }
 594}
 595
 596/*
 597 * A level in the reference hierarchy that is currently being iterated
 598 * through.
 599 */
 600struct cache_ref_iterator_level {
 601        /*
 602         * The ref_dir being iterated over at this level. The ref_dir
 603         * is sorted before being stored here.
 604         */
 605        struct ref_dir *dir;
 606
 607        /*
 608         * The index of the current entry within dir (which might
 609         * itself be a directory). If index == -1, then the iteration
 610         * hasn't yet begun. If index == dir->nr, then the iteration
 611         * through this level is over.
 612         */
 613        int index;
 614};
 615
 616/*
 617 * Represent an iteration through a ref_dir in the memory cache. The
 618 * iteration recurses through subdirectories.
 619 */
 620struct cache_ref_iterator {
 621        struct ref_iterator base;
 622
 623        /*
 624         * The number of levels currently on the stack. This is always
 625         * at least 1, because when it becomes zero the iteration is
 626         * ended and this struct is freed.
 627         */
 628        size_t levels_nr;
 629
 630        /* The number of levels that have been allocated on the stack */
 631        size_t levels_alloc;
 632
 633        /*
 634         * A stack of levels. levels[0] is the uppermost level that is
 635         * being iterated over in this iteration. (This is not
 636         * necessary the top level in the references hierarchy. If we
 637         * are iterating through a subtree, then levels[0] will hold
 638         * the ref_dir for that subtree, and subsequent levels will go
 639         * on from there.)
 640         */
 641        struct cache_ref_iterator_level *levels;
 642};
 643
 644static int cache_ref_iterator_advance(struct ref_iterator *ref_iterator)
 645{
 646        struct cache_ref_iterator *iter =
 647                (struct cache_ref_iterator *)ref_iterator;
 648
 649        while (1) {
 650                struct cache_ref_iterator_level *level =
 651                        &iter->levels[iter->levels_nr - 1];
 652                struct ref_dir *dir = level->dir;
 653                struct ref_entry *entry;
 654
 655                if (level->index == -1)
 656                        sort_ref_dir(dir);
 657
 658                if (++level->index == level->dir->nr) {
 659                        /* This level is exhausted; pop up a level */
 660                        if (--iter->levels_nr == 0)
 661                                return ref_iterator_abort(ref_iterator);
 662
 663                        continue;
 664                }
 665
 666                entry = dir->entries[level->index];
 667
 668                if (entry->flag & REF_DIR) {
 669                        /* push down a level */
 670                        ALLOC_GROW(iter->levels, iter->levels_nr + 1,
 671                                   iter->levels_alloc);
 672
 673                        level = &iter->levels[iter->levels_nr++];
 674                        level->dir = get_ref_dir(entry);
 675                        level->index = -1;
 676                } else {
 677                        iter->base.refname = entry->name;
 678                        iter->base.oid = &entry->u.value.oid;
 679                        iter->base.flags = entry->flag;
 680                        return ITER_OK;
 681                }
 682        }
 683}
 684
 685static enum peel_status peel_entry(struct ref_entry *entry, int repeel);
 686
 687static int cache_ref_iterator_peel(struct ref_iterator *ref_iterator,
 688                                   struct object_id *peeled)
 689{
 690        struct cache_ref_iterator *iter =
 691                (struct cache_ref_iterator *)ref_iterator;
 692        struct cache_ref_iterator_level *level;
 693        struct ref_entry *entry;
 694
 695        level = &iter->levels[iter->levels_nr - 1];
 696
 697        if (level->index == -1)
 698                die("BUG: peel called before advance for cache iterator");
 699
 700        entry = level->dir->entries[level->index];
 701
 702        if (peel_entry(entry, 0))
 703                return -1;
 704        oidcpy(peeled, &entry->u.value.peeled);
 705        return 0;
 706}
 707
 708static int cache_ref_iterator_abort(struct ref_iterator *ref_iterator)
 709{
 710        struct cache_ref_iterator *iter =
 711                (struct cache_ref_iterator *)ref_iterator;
 712
 713        free(iter->levels);
 714        base_ref_iterator_free(ref_iterator);
 715        return ITER_DONE;
 716}
 717
 718static struct ref_iterator_vtable cache_ref_iterator_vtable = {
 719        cache_ref_iterator_advance,
 720        cache_ref_iterator_peel,
 721        cache_ref_iterator_abort
 722};
 723
 724static struct ref_iterator *cache_ref_iterator_begin(struct ref_dir *dir)
 725{
 726        struct cache_ref_iterator *iter;
 727        struct ref_iterator *ref_iterator;
 728        struct cache_ref_iterator_level *level;
 729
 730        iter = xcalloc(1, sizeof(*iter));
 731        ref_iterator = &iter->base;
 732        base_ref_iterator_init(ref_iterator, &cache_ref_iterator_vtable);
 733        ALLOC_GROW(iter->levels, 10, iter->levels_alloc);
 734
 735        iter->levels_nr = 1;
 736        level = &iter->levels[0];
 737        level->index = -1;
 738        level->dir = dir;
 739
 740        return ref_iterator;
 741}
 742
 743struct nonmatching_ref_data {
 744        const struct string_list *skip;
 745        const char *conflicting_refname;
 746};
 747
 748static int nonmatching_ref_fn(struct ref_entry *entry, void *vdata)
 749{
 750        struct nonmatching_ref_data *data = vdata;
 751
 752        if (data->skip && string_list_has_string(data->skip, entry->name))
 753                return 0;
 754
 755        data->conflicting_refname = entry->name;
 756        return 1;
 757}
 758
 759/*
 760 * Return 0 if a reference named refname could be created without
 761 * conflicting with the name of an existing reference in dir.
 762 * See verify_refname_available for more information.
 763 */
 764static int verify_refname_available_dir(const char *refname,
 765                                        const struct string_list *extras,
 766                                        const struct string_list *skip,
 767                                        struct ref_dir *dir,
 768                                        struct strbuf *err)
 769{
 770        const char *slash;
 771        const char *extra_refname;
 772        int pos;
 773        struct strbuf dirname = STRBUF_INIT;
 774        int ret = -1;
 775
 776        /*
 777         * For the sake of comments in this function, suppose that
 778         * refname is "refs/foo/bar".
 779         */
 780
 781        assert(err);
 782
 783        strbuf_grow(&dirname, strlen(refname) + 1);
 784        for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) {
 785                /* Expand dirname to the new prefix, not including the trailing slash: */
 786                strbuf_add(&dirname, refname + dirname.len, slash - refname - dirname.len);
 787
 788                /*
 789                 * We are still at a leading dir of the refname (e.g.,
 790                 * "refs/foo"; if there is a reference with that name,
 791                 * it is a conflict, *unless* it is in skip.
 792                 */
 793                if (dir) {
 794                        pos = search_ref_dir(dir, dirname.buf, dirname.len);
 795                        if (pos >= 0 &&
 796                            (!skip || !string_list_has_string(skip, dirname.buf))) {
 797                                /*
 798                                 * We found a reference whose name is
 799                                 * a proper prefix of refname; e.g.,
 800                                 * "refs/foo", and is not in skip.
 801                                 */
 802                                strbuf_addf(err, "'%s' exists; cannot create '%s'",
 803                                            dirname.buf, refname);
 804                                goto cleanup;
 805                        }
 806                }
 807
 808                if (extras && string_list_has_string(extras, dirname.buf) &&
 809                    (!skip || !string_list_has_string(skip, dirname.buf))) {
 810                        strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
 811                                    refname, dirname.buf);
 812                        goto cleanup;
 813                }
 814
 815                /*
 816                 * Otherwise, we can try to continue our search with
 817                 * the next component. So try to look up the
 818                 * directory, e.g., "refs/foo/". If we come up empty,
 819                 * we know there is nothing under this whole prefix,
 820                 * but even in that case we still have to continue the
 821                 * search for conflicts with extras.
 822                 */
 823                strbuf_addch(&dirname, '/');
 824                if (dir) {
 825                        pos = search_ref_dir(dir, dirname.buf, dirname.len);
 826                        if (pos < 0) {
 827                                /*
 828                                 * There was no directory "refs/foo/",
 829                                 * so there is nothing under this
 830                                 * whole prefix. So there is no need
 831                                 * to continue looking for conflicting
 832                                 * references. But we need to continue
 833                                 * looking for conflicting extras.
 834                                 */
 835                                dir = NULL;
 836                        } else {
 837                                dir = get_ref_dir(dir->entries[pos]);
 838                        }
 839                }
 840        }
 841
 842        /*
 843         * We are at the leaf of our refname (e.g., "refs/foo/bar").
 844         * There is no point in searching for a reference with that
 845         * name, because a refname isn't considered to conflict with
 846         * itself. But we still need to check for references whose
 847         * names are in the "refs/foo/bar/" namespace, because they
 848         * *do* conflict.
 849         */
 850        strbuf_addstr(&dirname, refname + dirname.len);
 851        strbuf_addch(&dirname, '/');
 852
 853        if (dir) {
 854                pos = search_ref_dir(dir, dirname.buf, dirname.len);
 855
 856                if (pos >= 0) {
 857                        /*
 858                         * We found a directory named "$refname/"
 859                         * (e.g., "refs/foo/bar/"). It is a problem
 860                         * iff it contains any ref that is not in
 861                         * "skip".
 862                         */
 863                        struct nonmatching_ref_data data;
 864
 865                        data.skip = skip;
 866                        data.conflicting_refname = NULL;
 867                        dir = get_ref_dir(dir->entries[pos]);
 868                        sort_ref_dir(dir);
 869                        if (do_for_each_entry_in_dir(dir, 0, nonmatching_ref_fn, &data)) {
 870                                strbuf_addf(err, "'%s' exists; cannot create '%s'",
 871                                            data.conflicting_refname, refname);
 872                                goto cleanup;
 873                        }
 874                }
 875        }
 876
 877        extra_refname = find_descendant_ref(dirname.buf, extras, skip);
 878        if (extra_refname)
 879                strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
 880                            refname, extra_refname);
 881        else
 882                ret = 0;
 883
 884cleanup:
 885        strbuf_release(&dirname);
 886        return ret;
 887}
 888
 889struct packed_ref_cache {
 890        struct ref_entry *root;
 891
 892        /*
 893         * Count of references to the data structure in this instance,
 894         * including the pointer from files_ref_store::packed if any.
 895         * The data will not be freed as long as the reference count
 896         * is nonzero.
 897         */
 898        unsigned int referrers;
 899
 900        /*
 901         * Iff the packed-refs file associated with this instance is
 902         * currently locked for writing, this points at the associated
 903         * lock (which is owned by somebody else).  The referrer count
 904         * is also incremented when the file is locked and decremented
 905         * when it is unlocked.
 906         */
 907        struct lock_file *lock;
 908
 909        /* The metadata from when this packed-refs cache was read */
 910        struct stat_validity validity;
 911};
 912
 913/*
 914 * Future: need to be in "struct repository"
 915 * when doing a full libification.
 916 */
 917struct files_ref_store {
 918        struct ref_store base;
 919        unsigned int store_flags;
 920
 921        char *gitdir;
 922        char *gitcommondir;
 923        char *packed_refs_path;
 924
 925        struct ref_entry *loose;
 926        struct packed_ref_cache *packed;
 927};
 928
 929/* Lock used for the main packed-refs file: */
 930static struct lock_file packlock;
 931
 932/*
 933 * Increment the reference count of *packed_refs.
 934 */
 935static void acquire_packed_ref_cache(struct packed_ref_cache *packed_refs)
 936{
 937        packed_refs->referrers++;
 938}
 939
 940/*
 941 * Decrease the reference count of *packed_refs.  If it goes to zero,
 942 * free *packed_refs and return true; otherwise return false.
 943 */
 944static int release_packed_ref_cache(struct packed_ref_cache *packed_refs)
 945{
 946        if (!--packed_refs->referrers) {
 947                free_ref_entry(packed_refs->root);
 948                stat_validity_clear(&packed_refs->validity);
 949                free(packed_refs);
 950                return 1;
 951        } else {
 952                return 0;
 953        }
 954}
 955
 956static void clear_packed_ref_cache(struct files_ref_store *refs)
 957{
 958        if (refs->packed) {
 959                struct packed_ref_cache *packed_refs = refs->packed;
 960
 961                if (packed_refs->lock)
 962                        die("internal error: packed-ref cache cleared while locked");
 963                refs->packed = NULL;
 964                release_packed_ref_cache(packed_refs);
 965        }
 966}
 967
 968static void clear_loose_ref_cache(struct files_ref_store *refs)
 969{
 970        if (refs->loose) {
 971                free_ref_entry(refs->loose);
 972                refs->loose = NULL;
 973        }
 974}
 975
 976/*
 977 * Create a new submodule ref cache and add it to the internal
 978 * set of caches.
 979 */
 980static struct ref_store *files_ref_store_create(const char *gitdir,
 981                                                unsigned int flags)
 982{
 983        struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
 984        struct ref_store *ref_store = (struct ref_store *)refs;
 985        struct strbuf sb = STRBUF_INIT;
 986
 987        base_ref_store_init(ref_store, &refs_be_files);
 988        refs->store_flags = flags;
 989
 990        refs->gitdir = xstrdup(gitdir);
 991        get_common_dir_noenv(&sb, gitdir);
 992        refs->gitcommondir = strbuf_detach(&sb, NULL);
 993        strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
 994        refs->packed_refs_path = strbuf_detach(&sb, NULL);
 995
 996        return ref_store;
 997}
 998
 999/*
1000 * Die if refs is not the main ref store. caller is used in any
1001 * necessary error messages.
1002 */
1003static void files_assert_main_repository(struct files_ref_store *refs,
1004                                         const char *caller)
1005{
1006        if (refs->store_flags & REF_STORE_MAIN)
1007                return;
1008
1009        die("BUG: operation %s only allowed for main ref store", caller);
1010}
1011
1012/*
1013 * Downcast ref_store to files_ref_store. Die if ref_store is not a
1014 * files_ref_store. required_flags is compared with ref_store's
1015 * store_flags to ensure the ref_store has all required capabilities.
1016 * "caller" is used in any necessary error messages.
1017 */
1018static struct files_ref_store *files_downcast(struct ref_store *ref_store,
1019                                              unsigned int required_flags,
1020                                              const char *caller)
1021{
1022        struct files_ref_store *refs;
1023
1024        if (ref_store->be != &refs_be_files)
1025                die("BUG: ref_store is type \"%s\" not \"files\" in %s",
1026                    ref_store->be->name, caller);
1027
1028        refs = (struct files_ref_store *)ref_store;
1029
1030        if ((refs->store_flags & required_flags) != required_flags)
1031                die("BUG: operation %s requires abilities 0x%x, but only have 0x%x",
1032                    caller, required_flags, refs->store_flags);
1033
1034        return refs;
1035}
1036
1037/* The length of a peeled reference line in packed-refs, including EOL: */
1038#define PEELED_LINE_LENGTH 42
1039
1040/*
1041 * The packed-refs header line that we write out.  Perhaps other
1042 * traits will be added later.  The trailing space is required.
1043 */
1044static const char PACKED_REFS_HEADER[] =
1045        "# pack-refs with: peeled fully-peeled \n";
1046
1047/*
1048 * Parse one line from a packed-refs file.  Write the SHA1 to sha1.
1049 * Return a pointer to the refname within the line (null-terminated),
1050 * or NULL if there was a problem.
1051 */
1052static const char *parse_ref_line(struct strbuf *line, unsigned char *sha1)
1053{
1054        const char *ref;
1055
1056        /*
1057         * 42: the answer to everything.
1058         *
1059         * In this case, it happens to be the answer to
1060         *  40 (length of sha1 hex representation)
1061         *  +1 (space in between hex and name)
1062         *  +1 (newline at the end of the line)
1063         */
1064        if (line->len <= 42)
1065                return NULL;
1066
1067        if (get_sha1_hex(line->buf, sha1) < 0)
1068                return NULL;
1069        if (!isspace(line->buf[40]))
1070                return NULL;
1071
1072        ref = line->buf + 41;
1073        if (isspace(*ref))
1074                return NULL;
1075
1076        if (line->buf[line->len - 1] != '\n')
1077                return NULL;
1078        line->buf[--line->len] = 0;
1079
1080        return ref;
1081}
1082
1083/*
1084 * Read f, which is a packed-refs file, into dir.
1085 *
1086 * A comment line of the form "# pack-refs with: " may contain zero or
1087 * more traits. We interpret the traits as follows:
1088 *
1089 *   No traits:
1090 *
1091 *      Probably no references are peeled. But if the file contains a
1092 *      peeled value for a reference, we will use it.
1093 *
1094 *   peeled:
1095 *
1096 *      References under "refs/tags/", if they *can* be peeled, *are*
1097 *      peeled in this file. References outside of "refs/tags/" are
1098 *      probably not peeled even if they could have been, but if we find
1099 *      a peeled value for such a reference we will use it.
1100 *
1101 *   fully-peeled:
1102 *
1103 *      All references in the file that can be peeled are peeled.
1104 *      Inversely (and this is more important), any references in the
1105 *      file for which no peeled value is recorded is not peelable. This
1106 *      trait should typically be written alongside "peeled" for
1107 *      compatibility with older clients, but we do not require it
1108 *      (i.e., "peeled" is a no-op if "fully-peeled" is set).
1109 */
1110static void read_packed_refs(FILE *f, struct ref_dir *dir)
1111{
1112        struct ref_entry *last = NULL;
1113        struct strbuf line = STRBUF_INIT;
1114        enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled = PEELED_NONE;
1115
1116        while (strbuf_getwholeline(&line, f, '\n') != EOF) {
1117                unsigned char sha1[20];
1118                const char *refname;
1119                const char *traits;
1120
1121                if (skip_prefix(line.buf, "# pack-refs with:", &traits)) {
1122                        if (strstr(traits, " fully-peeled "))
1123                                peeled = PEELED_FULLY;
1124                        else if (strstr(traits, " peeled "))
1125                                peeled = PEELED_TAGS;
1126                        /* perhaps other traits later as well */
1127                        continue;
1128                }
1129
1130                refname = parse_ref_line(&line, sha1);
1131                if (refname) {
1132                        int flag = REF_ISPACKED;
1133
1134                        if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
1135                                if (!refname_is_safe(refname))
1136                                        die("packed refname is dangerous: %s", refname);
1137                                hashclr(sha1);
1138                                flag |= REF_BAD_NAME | REF_ISBROKEN;
1139                        }
1140                        last = create_ref_entry(refname, sha1, flag, 0);
1141                        if (peeled == PEELED_FULLY ||
1142                            (peeled == PEELED_TAGS && starts_with(refname, "refs/tags/")))
1143                                last->flag |= REF_KNOWS_PEELED;
1144                        add_ref(dir, last);
1145                        continue;
1146                }
1147                if (last &&
1148                    line.buf[0] == '^' &&
1149                    line.len == PEELED_LINE_LENGTH &&
1150                    line.buf[PEELED_LINE_LENGTH - 1] == '\n' &&
1151                    !get_sha1_hex(line.buf + 1, sha1)) {
1152                        hashcpy(last->u.value.peeled.hash, sha1);
1153                        /*
1154                         * Regardless of what the file header said,
1155                         * we definitely know the value of *this*
1156                         * reference:
1157                         */
1158                        last->flag |= REF_KNOWS_PEELED;
1159                }
1160        }
1161
1162        strbuf_release(&line);
1163}
1164
1165static const char *files_packed_refs_path(struct files_ref_store *refs)
1166{
1167        return refs->packed_refs_path;
1168}
1169
1170static void files_reflog_path(struct files_ref_store *refs,
1171                              struct strbuf *sb,
1172                              const char *refname)
1173{
1174        if (!refname) {
1175                /*
1176                 * FIXME: of course this is wrong in multi worktree
1177                 * setting. To be fixed real soon.
1178                 */
1179                strbuf_addf(sb, "%s/logs", refs->gitcommondir);
1180                return;
1181        }
1182
1183        switch (ref_type(refname)) {
1184        case REF_TYPE_PER_WORKTREE:
1185        case REF_TYPE_PSEUDOREF:
1186                strbuf_addf(sb, "%s/logs/%s", refs->gitdir, refname);
1187                break;
1188        case REF_TYPE_NORMAL:
1189                strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
1190                break;
1191        default:
1192                die("BUG: unknown ref type %d of ref %s",
1193                    ref_type(refname), refname);
1194        }
1195}
1196
1197static void files_ref_path(struct files_ref_store *refs,
1198                           struct strbuf *sb,
1199                           const char *refname)
1200{
1201        switch (ref_type(refname)) {
1202        case REF_TYPE_PER_WORKTREE:
1203        case REF_TYPE_PSEUDOREF:
1204                strbuf_addf(sb, "%s/%s", refs->gitdir, refname);
1205                break;
1206        case REF_TYPE_NORMAL:
1207                strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
1208                break;
1209        default:
1210                die("BUG: unknown ref type %d of ref %s",
1211                    ref_type(refname), refname);
1212        }
1213}
1214
1215/*
1216 * Get the packed_ref_cache for the specified files_ref_store,
1217 * creating it if necessary.
1218 */
1219static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *refs)
1220{
1221        const char *packed_refs_file = files_packed_refs_path(refs);
1222
1223        if (refs->packed &&
1224            !stat_validity_check(&refs->packed->validity, packed_refs_file))
1225                clear_packed_ref_cache(refs);
1226
1227        if (!refs->packed) {
1228                FILE *f;
1229
1230                refs->packed = xcalloc(1, sizeof(*refs->packed));
1231                acquire_packed_ref_cache(refs->packed);
1232                refs->packed->root = create_dir_entry(refs, "", 0, 0);
1233                f = fopen(packed_refs_file, "r");
1234                if (f) {
1235                        stat_validity_update(&refs->packed->validity, fileno(f));
1236                        read_packed_refs(f, get_ref_dir(refs->packed->root));
1237                        fclose(f);
1238                }
1239        }
1240        return refs->packed;
1241}
1242
1243static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_cache)
1244{
1245        return get_ref_dir(packed_ref_cache->root);
1246}
1247
1248static struct ref_dir *get_packed_refs(struct files_ref_store *refs)
1249{
1250        return get_packed_ref_dir(get_packed_ref_cache(refs));
1251}
1252
1253/*
1254 * Add a reference to the in-memory packed reference cache.  This may
1255 * only be called while the packed-refs file is locked (see
1256 * lock_packed_refs()).  To actually write the packed-refs file, call
1257 * commit_packed_refs().
1258 */
1259static void add_packed_ref(struct files_ref_store *refs,
1260                           const char *refname, const unsigned char *sha1)
1261{
1262        struct packed_ref_cache *packed_ref_cache = get_packed_ref_cache(refs);
1263
1264        if (!packed_ref_cache->lock)
1265                die("internal error: packed refs not locked");
1266        add_ref(get_packed_ref_dir(packed_ref_cache),
1267                create_ref_entry(refname, sha1, REF_ISPACKED, 1));
1268}
1269
1270/*
1271 * Read the loose references from the namespace dirname into dir
1272 * (without recursing).  dirname must end with '/'.  dir must be the
1273 * directory entry corresponding to dirname.
1274 */
1275static void read_loose_refs(const char *dirname, struct ref_dir *dir)
1276{
1277        struct files_ref_store *refs = dir->ref_store;
1278        DIR *d;
1279        struct dirent *de;
1280        int dirnamelen = strlen(dirname);
1281        struct strbuf refname;
1282        struct strbuf path = STRBUF_INIT;
1283        size_t path_baselen;
1284
1285        files_ref_path(refs, &path, dirname);
1286        path_baselen = path.len;
1287
1288        d = opendir(path.buf);
1289        if (!d) {
1290                strbuf_release(&path);
1291                return;
1292        }
1293
1294        strbuf_init(&refname, dirnamelen + 257);
1295        strbuf_add(&refname, dirname, dirnamelen);
1296
1297        while ((de = readdir(d)) != NULL) {
1298                unsigned char sha1[20];
1299                struct stat st;
1300                int flag;
1301
1302                if (de->d_name[0] == '.')
1303                        continue;
1304                if (ends_with(de->d_name, ".lock"))
1305                        continue;
1306                strbuf_addstr(&refname, de->d_name);
1307                strbuf_addstr(&path, de->d_name);
1308                if (stat(path.buf, &st) < 0) {
1309                        ; /* silently ignore */
1310                } else if (S_ISDIR(st.st_mode)) {
1311                        strbuf_addch(&refname, '/');
1312                        add_entry_to_dir(dir,
1313                                         create_dir_entry(refs, refname.buf,
1314                                                          refname.len, 1));
1315                } else {
1316                        if (!refs_resolve_ref_unsafe(&refs->base,
1317                                                     refname.buf,
1318                                                     RESOLVE_REF_READING,
1319                                                     sha1, &flag)) {
1320                                hashclr(sha1);
1321                                flag |= REF_ISBROKEN;
1322                        } else if (is_null_sha1(sha1)) {
1323                                /*
1324                                 * It is so astronomically unlikely
1325                                 * that NULL_SHA1 is the SHA-1 of an
1326                                 * actual object that we consider its
1327                                 * appearance in a loose reference
1328                                 * file to be repo corruption
1329                                 * (probably due to a software bug).
1330                                 */
1331                                flag |= REF_ISBROKEN;
1332                        }
1333
1334                        if (check_refname_format(refname.buf,
1335                                                 REFNAME_ALLOW_ONELEVEL)) {
1336                                if (!refname_is_safe(refname.buf))
1337                                        die("loose refname is dangerous: %s", refname.buf);
1338                                hashclr(sha1);
1339                                flag |= REF_BAD_NAME | REF_ISBROKEN;
1340                        }
1341                        add_entry_to_dir(dir,
1342                                         create_ref_entry(refname.buf, sha1, flag, 0));
1343                }
1344                strbuf_setlen(&refname, dirnamelen);
1345                strbuf_setlen(&path, path_baselen);
1346        }
1347        strbuf_release(&refname);
1348        strbuf_release(&path);
1349        closedir(d);
1350}
1351
1352static struct ref_dir *get_loose_refs(struct files_ref_store *refs)
1353{
1354        if (!refs->loose) {
1355                /*
1356                 * Mark the top-level directory complete because we
1357                 * are about to read the only subdirectory that can
1358                 * hold references:
1359                 */
1360                refs->loose = create_dir_entry(refs, "", 0, 0);
1361                /*
1362                 * Create an incomplete entry for "refs/":
1363                 */
1364                add_entry_to_dir(get_ref_dir(refs->loose),
1365                                 create_dir_entry(refs, "refs/", 5, 1));
1366        }
1367        return get_ref_dir(refs->loose);
1368}
1369
1370/*
1371 * Return the ref_entry for the given refname from the packed
1372 * references.  If it does not exist, return NULL.
1373 */
1374static struct ref_entry *get_packed_ref(struct files_ref_store *refs,
1375                                        const char *refname)
1376{
1377        return find_ref(get_packed_refs(refs), refname);
1378}
1379
1380/*
1381 * A loose ref file doesn't exist; check for a packed ref.
1382 */
1383static int resolve_packed_ref(struct files_ref_store *refs,
1384                              const char *refname,
1385                              unsigned char *sha1, unsigned int *flags)
1386{
1387        struct ref_entry *entry;
1388
1389        /*
1390         * The loose reference file does not exist; check for a packed
1391         * reference.
1392         */
1393        entry = get_packed_ref(refs, refname);
1394        if (entry) {
1395                hashcpy(sha1, entry->u.value.oid.hash);
1396                *flags |= REF_ISPACKED;
1397                return 0;
1398        }
1399        /* refname is not a packed reference. */
1400        return -1;
1401}
1402
1403static int files_read_raw_ref(struct ref_store *ref_store,
1404                              const char *refname, unsigned char *sha1,
1405                              struct strbuf *referent, unsigned int *type)
1406{
1407        struct files_ref_store *refs =
1408                files_downcast(ref_store, REF_STORE_READ, "read_raw_ref");
1409        struct strbuf sb_contents = STRBUF_INIT;
1410        struct strbuf sb_path = STRBUF_INIT;
1411        const char *path;
1412        const char *buf;
1413        struct stat st;
1414        int fd;
1415        int ret = -1;
1416        int save_errno;
1417        int remaining_retries = 3;
1418
1419        *type = 0;
1420        strbuf_reset(&sb_path);
1421
1422        files_ref_path(refs, &sb_path, refname);
1423
1424        path = sb_path.buf;
1425
1426stat_ref:
1427        /*
1428         * We might have to loop back here to avoid a race
1429         * condition: first we lstat() the file, then we try
1430         * to read it as a link or as a file.  But if somebody
1431         * changes the type of the file (file <-> directory
1432         * <-> symlink) between the lstat() and reading, then
1433         * we don't want to report that as an error but rather
1434         * try again starting with the lstat().
1435         *
1436         * We'll keep a count of the retries, though, just to avoid
1437         * any confusing situation sending us into an infinite loop.
1438         */
1439
1440        if (remaining_retries-- <= 0)
1441                goto out;
1442
1443        if (lstat(path, &st) < 0) {
1444                if (errno != ENOENT)
1445                        goto out;
1446                if (resolve_packed_ref(refs, refname, sha1, type)) {
1447                        errno = ENOENT;
1448                        goto out;
1449                }
1450                ret = 0;
1451                goto out;
1452        }
1453
1454        /* Follow "normalized" - ie "refs/.." symlinks by hand */
1455        if (S_ISLNK(st.st_mode)) {
1456                strbuf_reset(&sb_contents);
1457                if (strbuf_readlink(&sb_contents, path, 0) < 0) {
1458                        if (errno == ENOENT || errno == EINVAL)
1459                                /* inconsistent with lstat; retry */
1460                                goto stat_ref;
1461                        else
1462                                goto out;
1463                }
1464                if (starts_with(sb_contents.buf, "refs/") &&
1465                    !check_refname_format(sb_contents.buf, 0)) {
1466                        strbuf_swap(&sb_contents, referent);
1467                        *type |= REF_ISSYMREF;
1468                        ret = 0;
1469                        goto out;
1470                }
1471                /*
1472                 * It doesn't look like a refname; fall through to just
1473                 * treating it like a non-symlink, and reading whatever it
1474                 * points to.
1475                 */
1476        }
1477
1478        /* Is it a directory? */
1479        if (S_ISDIR(st.st_mode)) {
1480                /*
1481                 * Even though there is a directory where the loose
1482                 * ref is supposed to be, there could still be a
1483                 * packed ref:
1484                 */
1485                if (resolve_packed_ref(refs, refname, sha1, type)) {
1486                        errno = EISDIR;
1487                        goto out;
1488                }
1489                ret = 0;
1490                goto out;
1491        }
1492
1493        /*
1494         * Anything else, just open it and try to use it as
1495         * a ref
1496         */
1497        fd = open(path, O_RDONLY);
1498        if (fd < 0) {
1499                if (errno == ENOENT && !S_ISLNK(st.st_mode))
1500                        /* inconsistent with lstat; retry */
1501                        goto stat_ref;
1502                else
1503                        goto out;
1504        }
1505        strbuf_reset(&sb_contents);
1506        if (strbuf_read(&sb_contents, fd, 256) < 0) {
1507                int save_errno = errno;
1508                close(fd);
1509                errno = save_errno;
1510                goto out;
1511        }
1512        close(fd);
1513        strbuf_rtrim(&sb_contents);
1514        buf = sb_contents.buf;
1515        if (starts_with(buf, "ref:")) {
1516                buf += 4;
1517                while (isspace(*buf))
1518                        buf++;
1519
1520                strbuf_reset(referent);
1521                strbuf_addstr(referent, buf);
1522                *type |= REF_ISSYMREF;
1523                ret = 0;
1524                goto out;
1525        }
1526
1527        /*
1528         * Please note that FETCH_HEAD has additional
1529         * data after the sha.
1530         */
1531        if (get_sha1_hex(buf, sha1) ||
1532            (buf[40] != '\0' && !isspace(buf[40]))) {
1533                *type |= REF_ISBROKEN;
1534                errno = EINVAL;
1535                goto out;
1536        }
1537
1538        ret = 0;
1539
1540out:
1541        save_errno = errno;
1542        strbuf_release(&sb_path);
1543        strbuf_release(&sb_contents);
1544        errno = save_errno;
1545        return ret;
1546}
1547
1548static void unlock_ref(struct ref_lock *lock)
1549{
1550        /* Do not free lock->lk -- atexit() still looks at them */
1551        if (lock->lk)
1552                rollback_lock_file(lock->lk);
1553        free(lock->ref_name);
1554        free(lock);
1555}
1556
1557/*
1558 * Lock refname, without following symrefs, and set *lock_p to point
1559 * at a newly-allocated lock object. Fill in lock->old_oid, referent,
1560 * and type similarly to read_raw_ref().
1561 *
1562 * The caller must verify that refname is a "safe" reference name (in
1563 * the sense of refname_is_safe()) before calling this function.
1564 *
1565 * If the reference doesn't already exist, verify that refname doesn't
1566 * have a D/F conflict with any existing references. extras and skip
1567 * are passed to verify_refname_available_dir() for this check.
1568 *
1569 * If mustexist is not set and the reference is not found or is
1570 * broken, lock the reference anyway but clear sha1.
1571 *
1572 * Return 0 on success. On failure, write an error message to err and
1573 * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
1574 *
1575 * Implementation note: This function is basically
1576 *
1577 *     lock reference
1578 *     read_raw_ref()
1579 *
1580 * but it includes a lot more code to
1581 * - Deal with possible races with other processes
1582 * - Avoid calling verify_refname_available_dir() when it can be
1583 *   avoided, namely if we were successfully able to read the ref
1584 * - Generate informative error messages in the case of failure
1585 */
1586static int lock_raw_ref(struct files_ref_store *refs,
1587                        const char *refname, int mustexist,
1588                        const struct string_list *extras,
1589                        const struct string_list *skip,
1590                        struct ref_lock **lock_p,
1591                        struct strbuf *referent,
1592                        unsigned int *type,
1593                        struct strbuf *err)
1594{
1595        struct ref_lock *lock;
1596        struct strbuf ref_file = STRBUF_INIT;
1597        int attempts_remaining = 3;
1598        int ret = TRANSACTION_GENERIC_ERROR;
1599
1600        assert(err);
1601        files_assert_main_repository(refs, "lock_raw_ref");
1602
1603        *type = 0;
1604
1605        /* First lock the file so it can't change out from under us. */
1606
1607        *lock_p = lock = xcalloc(1, sizeof(*lock));
1608
1609        lock->ref_name = xstrdup(refname);
1610        files_ref_path(refs, &ref_file, refname);
1611
1612retry:
1613        switch (safe_create_leading_directories(ref_file.buf)) {
1614        case SCLD_OK:
1615                break; /* success */
1616        case SCLD_EXISTS:
1617                /*
1618                 * Suppose refname is "refs/foo/bar". We just failed
1619                 * to create the containing directory, "refs/foo",
1620                 * because there was a non-directory in the way. This
1621                 * indicates a D/F conflict, probably because of
1622                 * another reference such as "refs/foo". There is no
1623                 * reason to expect this error to be transitory.
1624                 */
1625                if (refs_verify_refname_available(&refs->base, refname,
1626                                                  extras, skip, err)) {
1627                        if (mustexist) {
1628                                /*
1629                                 * To the user the relevant error is
1630                                 * that the "mustexist" reference is
1631                                 * missing:
1632                                 */
1633                                strbuf_reset(err);
1634                                strbuf_addf(err, "unable to resolve reference '%s'",
1635                                            refname);
1636                        } else {
1637                                /*
1638                                 * The error message set by
1639                                 * verify_refname_available_dir() is OK.
1640                                 */
1641                                ret = TRANSACTION_NAME_CONFLICT;
1642                        }
1643                } else {
1644                        /*
1645                         * The file that is in the way isn't a loose
1646                         * reference. Report it as a low-level
1647                         * failure.
1648                         */
1649                        strbuf_addf(err, "unable to create lock file %s.lock; "
1650                                    "non-directory in the way",
1651                                    ref_file.buf);
1652                }
1653                goto error_return;
1654        case SCLD_VANISHED:
1655                /* Maybe another process was tidying up. Try again. */
1656                if (--attempts_remaining > 0)
1657                        goto retry;
1658                /* fall through */
1659        default:
1660                strbuf_addf(err, "unable to create directory for %s",
1661                            ref_file.buf);
1662                goto error_return;
1663        }
1664
1665        if (!lock->lk)
1666                lock->lk = xcalloc(1, sizeof(struct lock_file));
1667
1668        if (hold_lock_file_for_update(lock->lk, ref_file.buf, LOCK_NO_DEREF) < 0) {
1669                if (errno == ENOENT && --attempts_remaining > 0) {
1670                        /*
1671                         * Maybe somebody just deleted one of the
1672                         * directories leading to ref_file.  Try
1673                         * again:
1674                         */
1675                        goto retry;
1676                } else {
1677                        unable_to_lock_message(ref_file.buf, errno, err);
1678                        goto error_return;
1679                }
1680        }
1681
1682        /*
1683         * Now we hold the lock and can read the reference without
1684         * fear that its value will change.
1685         */
1686
1687        if (files_read_raw_ref(&refs->base, refname,
1688                               lock->old_oid.hash, referent, type)) {
1689                if (errno == ENOENT) {
1690                        if (mustexist) {
1691                                /* Garden variety missing reference. */
1692                                strbuf_addf(err, "unable to resolve reference '%s'",
1693                                            refname);
1694                                goto error_return;
1695                        } else {
1696                                /*
1697                                 * Reference is missing, but that's OK. We
1698                                 * know that there is not a conflict with
1699                                 * another loose reference because
1700                                 * (supposing that we are trying to lock
1701                                 * reference "refs/foo/bar"):
1702                                 *
1703                                 * - We were successfully able to create
1704                                 *   the lockfile refs/foo/bar.lock, so we
1705                                 *   know there cannot be a loose reference
1706                                 *   named "refs/foo".
1707                                 *
1708                                 * - We got ENOENT and not EISDIR, so we
1709                                 *   know that there cannot be a loose
1710                                 *   reference named "refs/foo/bar/baz".
1711                                 */
1712                        }
1713                } else if (errno == EISDIR) {
1714                        /*
1715                         * There is a directory in the way. It might have
1716                         * contained references that have been deleted. If
1717                         * we don't require that the reference already
1718                         * exists, try to remove the directory so that it
1719                         * doesn't cause trouble when we want to rename the
1720                         * lockfile into place later.
1721                         */
1722                        if (mustexist) {
1723                                /* Garden variety missing reference. */
1724                                strbuf_addf(err, "unable to resolve reference '%s'",
1725                                            refname);
1726                                goto error_return;
1727                        } else if (remove_dir_recursively(&ref_file,
1728                                                          REMOVE_DIR_EMPTY_ONLY)) {
1729                                if (verify_refname_available_dir(
1730                                                    refname, extras, skip,
1731                                                    get_loose_refs(refs),
1732                                                    err)) {
1733                                        /*
1734                                         * The error message set by
1735                                         * verify_refname_available() is OK.
1736                                         */
1737                                        ret = TRANSACTION_NAME_CONFLICT;
1738                                        goto error_return;
1739                                } else {
1740                                        /*
1741                                         * We can't delete the directory,
1742                                         * but we also don't know of any
1743                                         * references that it should
1744                                         * contain.
1745                                         */
1746                                        strbuf_addf(err, "there is a non-empty directory '%s' "
1747                                                    "blocking reference '%s'",
1748                                                    ref_file.buf, refname);
1749                                        goto error_return;
1750                                }
1751                        }
1752                } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
1753                        strbuf_addf(err, "unable to resolve reference '%s': "
1754                                    "reference broken", refname);
1755                        goto error_return;
1756                } else {
1757                        strbuf_addf(err, "unable to resolve reference '%s': %s",
1758                                    refname, strerror(errno));
1759                        goto error_return;
1760                }
1761
1762                /*
1763                 * If the ref did not exist and we are creating it,
1764                 * make sure there is no existing packed ref whose
1765                 * name begins with our refname, nor a packed ref
1766                 * whose name is a proper prefix of our refname.
1767                 */
1768                if (verify_refname_available_dir(
1769                                    refname, extras, skip,
1770                                    get_packed_refs(refs),
1771                                    err)) {
1772                        goto error_return;
1773                }
1774        }
1775
1776        ret = 0;
1777        goto out;
1778
1779error_return:
1780        unlock_ref(lock);
1781        *lock_p = NULL;
1782
1783out:
1784        strbuf_release(&ref_file);
1785        return ret;
1786}
1787
1788/*
1789 * Peel the entry (if possible) and return its new peel_status.  If
1790 * repeel is true, re-peel the entry even if there is an old peeled
1791 * value that is already stored in it.
1792 *
1793 * It is OK to call this function with a packed reference entry that
1794 * might be stale and might even refer to an object that has since
1795 * been garbage-collected.  In such a case, if the entry has
1796 * REF_KNOWS_PEELED then leave the status unchanged and return
1797 * PEEL_PEELED or PEEL_NON_TAG; otherwise, return PEEL_INVALID.
1798 */
1799static enum peel_status peel_entry(struct ref_entry *entry, int repeel)
1800{
1801        enum peel_status status;
1802
1803        if (entry->flag & REF_KNOWS_PEELED) {
1804                if (repeel) {
1805                        entry->flag &= ~REF_KNOWS_PEELED;
1806                        oidclr(&entry->u.value.peeled);
1807                } else {
1808                        return is_null_oid(&entry->u.value.peeled) ?
1809                                PEEL_NON_TAG : PEEL_PEELED;
1810                }
1811        }
1812        if (entry->flag & REF_ISBROKEN)
1813                return PEEL_BROKEN;
1814        if (entry->flag & REF_ISSYMREF)
1815                return PEEL_IS_SYMREF;
1816
1817        status = peel_object(entry->u.value.oid.hash, entry->u.value.peeled.hash);
1818        if (status == PEEL_PEELED || status == PEEL_NON_TAG)
1819                entry->flag |= REF_KNOWS_PEELED;
1820        return status;
1821}
1822
1823static int files_peel_ref(struct ref_store *ref_store,
1824                          const char *refname, unsigned char *sha1)
1825{
1826        struct files_ref_store *refs =
1827                files_downcast(ref_store, REF_STORE_READ | REF_STORE_ODB,
1828                               "peel_ref");
1829        int flag;
1830        unsigned char base[20];
1831
1832        if (current_ref_iter && current_ref_iter->refname == refname) {
1833                struct object_id peeled;
1834
1835                if (ref_iterator_peel(current_ref_iter, &peeled))
1836                        return -1;
1837                hashcpy(sha1, peeled.hash);
1838                return 0;
1839        }
1840
1841        if (refs_read_ref_full(ref_store, refname,
1842                               RESOLVE_REF_READING, base, &flag))
1843                return -1;
1844
1845        /*
1846         * If the reference is packed, read its ref_entry from the
1847         * cache in the hope that we already know its peeled value.
1848         * We only try this optimization on packed references because
1849         * (a) forcing the filling of the loose reference cache could
1850         * be expensive and (b) loose references anyway usually do not
1851         * have REF_KNOWS_PEELED.
1852         */
1853        if (flag & REF_ISPACKED) {
1854                struct ref_entry *r = get_packed_ref(refs, refname);
1855                if (r) {
1856                        if (peel_entry(r, 0))
1857                                return -1;
1858                        hashcpy(sha1, r->u.value.peeled.hash);
1859                        return 0;
1860                }
1861        }
1862
1863        return peel_object(base, sha1);
1864}
1865
1866struct files_ref_iterator {
1867        struct ref_iterator base;
1868
1869        struct packed_ref_cache *packed_ref_cache;
1870        struct ref_iterator *iter0;
1871        unsigned int flags;
1872};
1873
1874static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
1875{
1876        struct files_ref_iterator *iter =
1877                (struct files_ref_iterator *)ref_iterator;
1878        int ok;
1879
1880        while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
1881                if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
1882                    ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
1883                        continue;
1884
1885                if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
1886                    !ref_resolves_to_object(iter->iter0->refname,
1887                                            iter->iter0->oid,
1888                                            iter->iter0->flags))
1889                        continue;
1890
1891                iter->base.refname = iter->iter0->refname;
1892                iter->base.oid = iter->iter0->oid;
1893                iter->base.flags = iter->iter0->flags;
1894                return ITER_OK;
1895        }
1896
1897        iter->iter0 = NULL;
1898        if (ref_iterator_abort(ref_iterator) != ITER_DONE)
1899                ok = ITER_ERROR;
1900
1901        return ok;
1902}
1903
1904static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
1905                                   struct object_id *peeled)
1906{
1907        struct files_ref_iterator *iter =
1908                (struct files_ref_iterator *)ref_iterator;
1909
1910        return ref_iterator_peel(iter->iter0, peeled);
1911}
1912
1913static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
1914{
1915        struct files_ref_iterator *iter =
1916                (struct files_ref_iterator *)ref_iterator;
1917        int ok = ITER_DONE;
1918
1919        if (iter->iter0)
1920                ok = ref_iterator_abort(iter->iter0);
1921
1922        release_packed_ref_cache(iter->packed_ref_cache);
1923        base_ref_iterator_free(ref_iterator);
1924        return ok;
1925}
1926
1927static struct ref_iterator_vtable files_ref_iterator_vtable = {
1928        files_ref_iterator_advance,
1929        files_ref_iterator_peel,
1930        files_ref_iterator_abort
1931};
1932
1933static struct ref_iterator *files_ref_iterator_begin(
1934                struct ref_store *ref_store,
1935                const char *prefix, unsigned int flags)
1936{
1937        struct files_ref_store *refs;
1938        struct ref_dir *loose_dir, *packed_dir;
1939        struct ref_iterator *loose_iter, *packed_iter;
1940        struct files_ref_iterator *iter;
1941        struct ref_iterator *ref_iterator;
1942
1943        if (ref_paranoia < 0)
1944                ref_paranoia = git_env_bool("GIT_REF_PARANOIA", 0);
1945        if (ref_paranoia)
1946                flags |= DO_FOR_EACH_INCLUDE_BROKEN;
1947
1948        refs = files_downcast(ref_store,
1949                              REF_STORE_READ | (ref_paranoia ? 0 : REF_STORE_ODB),
1950                              "ref_iterator_begin");
1951
1952        iter = xcalloc(1, sizeof(*iter));
1953        ref_iterator = &iter->base;
1954        base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable);
1955
1956        /*
1957         * We must make sure that all loose refs are read before
1958         * accessing the packed-refs file; this avoids a race
1959         * condition if loose refs are migrated to the packed-refs
1960         * file by a simultaneous process, but our in-memory view is
1961         * from before the migration. We ensure this as follows:
1962         * First, we call prime_ref_dir(), which pre-reads the loose
1963         * references for the subtree into the cache. (If they've
1964         * already been read, that's OK; we only need to guarantee
1965         * that they're read before the packed refs, not *how much*
1966         * before.) After that, we call get_packed_ref_cache(), which
1967         * internally checks whether the packed-ref cache is up to
1968         * date with what is on disk, and re-reads it if not.
1969         */
1970
1971        loose_dir = get_loose_refs(refs);
1972
1973        if (prefix && *prefix)
1974                loose_dir = find_containing_dir(loose_dir, prefix, 0);
1975
1976        if (loose_dir) {
1977                prime_ref_dir(loose_dir);
1978                loose_iter = cache_ref_iterator_begin(loose_dir);
1979        } else {
1980                /* There's nothing to iterate over. */
1981                loose_iter = empty_ref_iterator_begin();
1982        }
1983
1984        iter->packed_ref_cache = get_packed_ref_cache(refs);
1985        acquire_packed_ref_cache(iter->packed_ref_cache);
1986        packed_dir = get_packed_ref_dir(iter->packed_ref_cache);
1987
1988        if (prefix && *prefix)
1989                packed_dir = find_containing_dir(packed_dir, prefix, 0);
1990
1991        if (packed_dir) {
1992                packed_iter = cache_ref_iterator_begin(packed_dir);
1993        } else {
1994                /* There's nothing to iterate over. */
1995                packed_iter = empty_ref_iterator_begin();
1996        }
1997
1998        iter->iter0 = overlay_ref_iterator_begin(loose_iter, packed_iter);
1999        iter->flags = flags;
2000
2001        return ref_iterator;
2002}
2003
2004/*
2005 * Verify that the reference locked by lock has the value old_sha1.
2006 * Fail if the reference doesn't exist and mustexist is set. Return 0
2007 * on success. On error, write an error message to err, set errno, and
2008 * return a negative value.
2009 */
2010static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
2011                       const unsigned char *old_sha1, int mustexist,
2012                       struct strbuf *err)
2013{
2014        assert(err);
2015
2016        if (refs_read_ref_full(ref_store, lock->ref_name,
2017                               mustexist ? RESOLVE_REF_READING : 0,
2018                               lock->old_oid.hash, NULL)) {
2019                if (old_sha1) {
2020                        int save_errno = errno;
2021                        strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
2022                        errno = save_errno;
2023                        return -1;
2024                } else {
2025                        oidclr(&lock->old_oid);
2026                        return 0;
2027                }
2028        }
2029        if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
2030                strbuf_addf(err, "ref '%s' is at %s but expected %s",
2031                            lock->ref_name,
2032                            oid_to_hex(&lock->old_oid),
2033                            sha1_to_hex(old_sha1));
2034                errno = EBUSY;
2035                return -1;
2036        }
2037        return 0;
2038}
2039
2040static int remove_empty_directories(struct strbuf *path)
2041{
2042        /*
2043         * we want to create a file but there is a directory there;
2044         * if that is an empty directory (or a directory that contains
2045         * only empty directories), remove them.
2046         */
2047        return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
2048}
2049
2050static int create_reflock(const char *path, void *cb)
2051{
2052        struct lock_file *lk = cb;
2053
2054        return hold_lock_file_for_update(lk, path, LOCK_NO_DEREF) < 0 ? -1 : 0;
2055}
2056
2057/*
2058 * Locks a ref returning the lock on success and NULL on failure.
2059 * On failure errno is set to something meaningful.
2060 */
2061static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
2062                                            const char *refname,
2063                                            const unsigned char *old_sha1,
2064                                            const struct string_list *extras,
2065                                            const struct string_list *skip,
2066                                            unsigned int flags, int *type,
2067                                            struct strbuf *err)
2068{
2069        struct strbuf ref_file = STRBUF_INIT;
2070        struct ref_lock *lock;
2071        int last_errno = 0;
2072        int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
2073        int resolve_flags = RESOLVE_REF_NO_RECURSE;
2074        int resolved;
2075
2076        files_assert_main_repository(refs, "lock_ref_sha1_basic");
2077        assert(err);
2078
2079        lock = xcalloc(1, sizeof(struct ref_lock));
2080
2081        if (mustexist)
2082                resolve_flags |= RESOLVE_REF_READING;
2083        if (flags & REF_DELETING)
2084                resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
2085
2086        files_ref_path(refs, &ref_file, refname);
2087        resolved = !!refs_resolve_ref_unsafe(&refs->base,
2088                                             refname, resolve_flags,
2089                                             lock->old_oid.hash, type);
2090        if (!resolved && errno == EISDIR) {
2091                /*
2092                 * we are trying to lock foo but we used to
2093                 * have foo/bar which now does not exist;
2094                 * it is normal for the empty directory 'foo'
2095                 * to remain.
2096                 */
2097                if (remove_empty_directories(&ref_file)) {
2098                        last_errno = errno;
2099                        if (!verify_refname_available_dir(
2100                                            refname, extras, skip,
2101                                            get_loose_refs(refs), err))
2102                                strbuf_addf(err, "there are still refs under '%s'",
2103                                            refname);
2104                        goto error_return;
2105                }
2106                resolved = !!refs_resolve_ref_unsafe(&refs->base,
2107                                                     refname, resolve_flags,
2108                                                     lock->old_oid.hash, type);
2109        }
2110        if (!resolved) {
2111                last_errno = errno;
2112                if (last_errno != ENOTDIR ||
2113                    !verify_refname_available_dir(
2114                                    refname, extras, skip,
2115                                    get_loose_refs(refs), err))
2116                        strbuf_addf(err, "unable to resolve reference '%s': %s",
2117                                    refname, strerror(last_errno));
2118
2119                goto error_return;
2120        }
2121
2122        /*
2123         * If the ref did not exist and we are creating it, make sure
2124         * there is no existing packed ref whose name begins with our
2125         * refname, nor a packed ref whose name is a proper prefix of
2126         * our refname.
2127         */
2128        if (is_null_oid(&lock->old_oid) &&
2129            verify_refname_available_dir(refname, extras, skip,
2130                                         get_packed_refs(refs),
2131                                         err)) {
2132                last_errno = ENOTDIR;
2133                goto error_return;
2134        }
2135
2136        lock->lk = xcalloc(1, sizeof(struct lock_file));
2137
2138        lock->ref_name = xstrdup(refname);
2139
2140        if (raceproof_create_file(ref_file.buf, create_reflock, lock->lk)) {
2141                last_errno = errno;
2142                unable_to_lock_message(ref_file.buf, errno, err);
2143                goto error_return;
2144        }
2145
2146        if (verify_lock(&refs->base, lock, old_sha1, mustexist, err)) {
2147                last_errno = errno;
2148                goto error_return;
2149        }
2150        goto out;
2151
2152 error_return:
2153        unlock_ref(lock);
2154        lock = NULL;
2155
2156 out:
2157        strbuf_release(&ref_file);
2158        errno = last_errno;
2159        return lock;
2160}
2161
2162/*
2163 * Write an entry to the packed-refs file for the specified refname.
2164 * If peeled is non-NULL, write it as the entry's peeled value.
2165 */
2166static void write_packed_entry(FILE *fh, char *refname, unsigned char *sha1,
2167                               unsigned char *peeled)
2168{
2169        fprintf_or_die(fh, "%s %s\n", sha1_to_hex(sha1), refname);
2170        if (peeled)
2171                fprintf_or_die(fh, "^%s\n", sha1_to_hex(peeled));
2172}
2173
2174/*
2175 * An each_ref_entry_fn that writes the entry to a packed-refs file.
2176 */
2177static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
2178{
2179        enum peel_status peel_status = peel_entry(entry, 0);
2180
2181        if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
2182                error("internal error: %s is not a valid packed reference!",
2183                      entry->name);
2184        write_packed_entry(cb_data, entry->name, entry->u.value.oid.hash,
2185                           peel_status == PEEL_PEELED ?
2186                           entry->u.value.peeled.hash : NULL);
2187        return 0;
2188}
2189
2190/*
2191 * Lock the packed-refs file for writing. Flags is passed to
2192 * hold_lock_file_for_update(). Return 0 on success. On errors, set
2193 * errno appropriately and return a nonzero value.
2194 */
2195static int lock_packed_refs(struct files_ref_store *refs, int flags)
2196{
2197        static int timeout_configured = 0;
2198        static int timeout_value = 1000;
2199        struct packed_ref_cache *packed_ref_cache;
2200
2201        files_assert_main_repository(refs, "lock_packed_refs");
2202
2203        if (!timeout_configured) {
2204                git_config_get_int("core.packedrefstimeout", &timeout_value);
2205                timeout_configured = 1;
2206        }
2207
2208        if (hold_lock_file_for_update_timeout(
2209                            &packlock, files_packed_refs_path(refs),
2210                            flags, timeout_value) < 0)
2211                return -1;
2212        /*
2213         * Get the current packed-refs while holding the lock.  If the
2214         * packed-refs file has been modified since we last read it,
2215         * this will automatically invalidate the cache and re-read
2216         * the packed-refs file.
2217         */
2218        packed_ref_cache = get_packed_ref_cache(refs);
2219        packed_ref_cache->lock = &packlock;
2220        /* Increment the reference count to prevent it from being freed: */
2221        acquire_packed_ref_cache(packed_ref_cache);
2222        return 0;
2223}
2224
2225/*
2226 * Write the current version of the packed refs cache from memory to
2227 * disk. The packed-refs file must already be locked for writing (see
2228 * lock_packed_refs()). Return zero on success. On errors, set errno
2229 * and return a nonzero value
2230 */
2231static int commit_packed_refs(struct files_ref_store *refs)
2232{
2233        struct packed_ref_cache *packed_ref_cache =
2234                get_packed_ref_cache(refs);
2235        int error = 0;
2236        int save_errno = 0;
2237        FILE *out;
2238
2239        files_assert_main_repository(refs, "commit_packed_refs");
2240
2241        if (!packed_ref_cache->lock)
2242                die("internal error: packed-refs not locked");
2243
2244        out = fdopen_lock_file(packed_ref_cache->lock, "w");
2245        if (!out)
2246                die_errno("unable to fdopen packed-refs descriptor");
2247
2248        fprintf_or_die(out, "%s", PACKED_REFS_HEADER);
2249        do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
2250                                 0, write_packed_entry_fn, out);
2251
2252        if (commit_lock_file(packed_ref_cache->lock)) {
2253                save_errno = errno;
2254                error = -1;
2255        }
2256        packed_ref_cache->lock = NULL;
2257        release_packed_ref_cache(packed_ref_cache);
2258        errno = save_errno;
2259        return error;
2260}
2261
2262/*
2263 * Rollback the lockfile for the packed-refs file, and discard the
2264 * in-memory packed reference cache.  (The packed-refs file will be
2265 * read anew if it is needed again after this function is called.)
2266 */
2267static void rollback_packed_refs(struct files_ref_store *refs)
2268{
2269        struct packed_ref_cache *packed_ref_cache =
2270                get_packed_ref_cache(refs);
2271
2272        files_assert_main_repository(refs, "rollback_packed_refs");
2273
2274        if (!packed_ref_cache->lock)
2275                die("internal error: packed-refs not locked");
2276        rollback_lock_file(packed_ref_cache->lock);
2277        packed_ref_cache->lock = NULL;
2278        release_packed_ref_cache(packed_ref_cache);
2279        clear_packed_ref_cache(refs);
2280}
2281
2282struct ref_to_prune {
2283        struct ref_to_prune *next;
2284        unsigned char sha1[20];
2285        char name[FLEX_ARRAY];
2286};
2287
2288struct pack_refs_cb_data {
2289        unsigned int flags;
2290        struct ref_dir *packed_refs;
2291        struct ref_to_prune *ref_to_prune;
2292};
2293
2294/*
2295 * An each_ref_entry_fn that is run over loose references only.  If
2296 * the loose reference can be packed, add an entry in the packed ref
2297 * cache.  If the reference should be pruned, also add it to
2298 * ref_to_prune in the pack_refs_cb_data.
2299 */
2300static int pack_if_possible_fn(struct ref_entry *entry, void *cb_data)
2301{
2302        struct pack_refs_cb_data *cb = cb_data;
2303        enum peel_status peel_status;
2304        struct ref_entry *packed_entry;
2305        int is_tag_ref = starts_with(entry->name, "refs/tags/");
2306
2307        /* Do not pack per-worktree refs: */
2308        if (ref_type(entry->name) != REF_TYPE_NORMAL)
2309                return 0;
2310
2311        /* ALWAYS pack tags */
2312        if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref)
2313                return 0;
2314
2315        /* Do not pack symbolic or broken refs: */
2316        if ((entry->flag & REF_ISSYMREF) || !entry_resolves_to_object(entry))
2317                return 0;
2318
2319        /* Add a packed ref cache entry equivalent to the loose entry. */
2320        peel_status = peel_entry(entry, 1);
2321        if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
2322                die("internal error peeling reference %s (%s)",
2323                    entry->name, oid_to_hex(&entry->u.value.oid));
2324        packed_entry = find_ref(cb->packed_refs, entry->name);
2325        if (packed_entry) {
2326                /* Overwrite existing packed entry with info from loose entry */
2327                packed_entry->flag = REF_ISPACKED | REF_KNOWS_PEELED;
2328                oidcpy(&packed_entry->u.value.oid, &entry->u.value.oid);
2329        } else {
2330                packed_entry = create_ref_entry(entry->name, entry->u.value.oid.hash,
2331                                                REF_ISPACKED | REF_KNOWS_PEELED, 0);
2332                add_ref(cb->packed_refs, packed_entry);
2333        }
2334        oidcpy(&packed_entry->u.value.peeled, &entry->u.value.peeled);
2335
2336        /* Schedule the loose reference for pruning if requested. */
2337        if ((cb->flags & PACK_REFS_PRUNE)) {
2338                struct ref_to_prune *n;
2339                FLEX_ALLOC_STR(n, name, entry->name);
2340                hashcpy(n->sha1, entry->u.value.oid.hash);
2341                n->next = cb->ref_to_prune;
2342                cb->ref_to_prune = n;
2343        }
2344        return 0;
2345}
2346
2347enum {
2348        REMOVE_EMPTY_PARENTS_REF = 0x01,
2349        REMOVE_EMPTY_PARENTS_REFLOG = 0x02
2350};
2351
2352/*
2353 * Remove empty parent directories associated with the specified
2354 * reference and/or its reflog, but spare [logs/]refs/ and immediate
2355 * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
2356 * REMOVE_EMPTY_PARENTS_REFLOG.
2357 */
2358static void try_remove_empty_parents(struct files_ref_store *refs,
2359                                     const char *refname,
2360                                     unsigned int flags)
2361{
2362        struct strbuf buf = STRBUF_INIT;
2363        struct strbuf sb = STRBUF_INIT;
2364        char *p, *q;
2365        int i;
2366
2367        strbuf_addstr(&buf, refname);
2368        p = buf.buf;
2369        for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
2370                while (*p && *p != '/')
2371                        p++;
2372                /* tolerate duplicate slashes; see check_refname_format() */
2373                while (*p == '/')
2374                        p++;
2375        }
2376        q = buf.buf + buf.len;
2377        while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
2378                while (q > p && *q != '/')
2379                        q--;
2380                while (q > p && *(q-1) == '/')
2381                        q--;
2382                if (q == p)
2383                        break;
2384                strbuf_setlen(&buf, q - buf.buf);
2385
2386                strbuf_reset(&sb);
2387                files_ref_path(refs, &sb, buf.buf);
2388                if ((flags & REMOVE_EMPTY_PARENTS_REF) && rmdir(sb.buf))
2389                        flags &= ~REMOVE_EMPTY_PARENTS_REF;
2390
2391                strbuf_reset(&sb);
2392                files_reflog_path(refs, &sb, buf.buf);
2393                if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) && rmdir(sb.buf))
2394                        flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
2395        }
2396        strbuf_release(&buf);
2397        strbuf_release(&sb);
2398}
2399
2400/* make sure nobody touched the ref, and unlink */
2401static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
2402{
2403        struct ref_transaction *transaction;
2404        struct strbuf err = STRBUF_INIT;
2405
2406        if (check_refname_format(r->name, 0))
2407                return;
2408
2409        transaction = ref_store_transaction_begin(&refs->base, &err);
2410        if (!transaction ||
2411            ref_transaction_delete(transaction, r->name, r->sha1,
2412                                   REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
2413            ref_transaction_commit(transaction, &err)) {
2414                ref_transaction_free(transaction);
2415                error("%s", err.buf);
2416                strbuf_release(&err);
2417                return;
2418        }
2419        ref_transaction_free(transaction);
2420        strbuf_release(&err);
2421}
2422
2423static void prune_refs(struct files_ref_store *refs, struct ref_to_prune *r)
2424{
2425        while (r) {
2426                prune_ref(refs, r);
2427                r = r->next;
2428        }
2429}
2430
2431static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
2432{
2433        struct files_ref_store *refs =
2434                files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
2435                               "pack_refs");
2436        struct pack_refs_cb_data cbdata;
2437
2438        memset(&cbdata, 0, sizeof(cbdata));
2439        cbdata.flags = flags;
2440
2441        lock_packed_refs(refs, LOCK_DIE_ON_ERROR);
2442        cbdata.packed_refs = get_packed_refs(refs);
2443
2444        do_for_each_entry_in_dir(get_loose_refs(refs), 0,
2445                                 pack_if_possible_fn, &cbdata);
2446
2447        if (commit_packed_refs(refs))
2448                die_errno("unable to overwrite old ref-pack file");
2449
2450        prune_refs(refs, cbdata.ref_to_prune);
2451        return 0;
2452}
2453
2454/*
2455 * Rewrite the packed-refs file, omitting any refs listed in
2456 * 'refnames'. On error, leave packed-refs unchanged, write an error
2457 * message to 'err', and return a nonzero value.
2458 *
2459 * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
2460 */
2461static int repack_without_refs(struct files_ref_store *refs,
2462                               struct string_list *refnames, struct strbuf *err)
2463{
2464        struct ref_dir *packed;
2465        struct string_list_item *refname;
2466        int ret, needs_repacking = 0, removed = 0;
2467
2468        files_assert_main_repository(refs, "repack_without_refs");
2469        assert(err);
2470
2471        /* Look for a packed ref */
2472        for_each_string_list_item(refname, refnames) {
2473                if (get_packed_ref(refs, refname->string)) {
2474                        needs_repacking = 1;
2475                        break;
2476                }
2477        }
2478
2479        /* Avoid locking if we have nothing to do */
2480        if (!needs_repacking)
2481                return 0; /* no refname exists in packed refs */
2482
2483        if (lock_packed_refs(refs, 0)) {
2484                unable_to_lock_message(files_packed_refs_path(refs), errno, err);
2485                return -1;
2486        }
2487        packed = get_packed_refs(refs);
2488
2489        /* Remove refnames from the cache */
2490        for_each_string_list_item(refname, refnames)
2491                if (remove_entry(packed, refname->string) != -1)
2492                        removed = 1;
2493        if (!removed) {
2494                /*
2495                 * All packed entries disappeared while we were
2496                 * acquiring the lock.
2497                 */
2498                rollback_packed_refs(refs);
2499                return 0;
2500        }
2501
2502        /* Write what remains */
2503        ret = commit_packed_refs(refs);
2504        if (ret)
2505                strbuf_addf(err, "unable to overwrite old ref-pack file: %s",
2506                            strerror(errno));
2507        return ret;
2508}
2509
2510static int files_delete_refs(struct ref_store *ref_store,
2511                             struct string_list *refnames, unsigned int flags)
2512{
2513        struct files_ref_store *refs =
2514                files_downcast(ref_store, REF_STORE_WRITE, "delete_refs");
2515        struct strbuf err = STRBUF_INIT;
2516        int i, result = 0;
2517
2518        if (!refnames->nr)
2519                return 0;
2520
2521        result = repack_without_refs(refs, refnames, &err);
2522        if (result) {
2523                /*
2524                 * If we failed to rewrite the packed-refs file, then
2525                 * it is unsafe to try to remove loose refs, because
2526                 * doing so might expose an obsolete packed value for
2527                 * a reference that might even point at an object that
2528                 * has been garbage collected.
2529                 */
2530                if (refnames->nr == 1)
2531                        error(_("could not delete reference %s: %s"),
2532                              refnames->items[0].string, err.buf);
2533                else
2534                        error(_("could not delete references: %s"), err.buf);
2535
2536                goto out;
2537        }
2538
2539        for (i = 0; i < refnames->nr; i++) {
2540                const char *refname = refnames->items[i].string;
2541
2542                if (refs_delete_ref(&refs->base, NULL, refname, NULL, flags))
2543                        result |= error(_("could not remove reference %s"), refname);
2544        }
2545
2546out:
2547        strbuf_release(&err);
2548        return result;
2549}
2550
2551/*
2552 * People using contrib's git-new-workdir have .git/logs/refs ->
2553 * /some/other/path/.git/logs/refs, and that may live on another device.
2554 *
2555 * IOW, to avoid cross device rename errors, the temporary renamed log must
2556 * live into logs/refs.
2557 */
2558#define TMP_RENAMED_LOG  "refs/.tmp-renamed-log"
2559
2560struct rename_cb {
2561        const char *tmp_renamed_log;
2562        int true_errno;
2563};
2564
2565static int rename_tmp_log_callback(const char *path, void *cb_data)
2566{
2567        struct rename_cb *cb = cb_data;
2568
2569        if (rename(cb->tmp_renamed_log, path)) {
2570                /*
2571                 * rename(a, b) when b is an existing directory ought
2572                 * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
2573                 * Sheesh. Record the true errno for error reporting,
2574                 * but report EISDIR to raceproof_create_file() so
2575                 * that it knows to retry.
2576                 */
2577                cb->true_errno = errno;
2578                if (errno == ENOTDIR)
2579                        errno = EISDIR;
2580                return -1;
2581        } else {
2582                return 0;
2583        }
2584}
2585
2586static int rename_tmp_log(struct files_ref_store *refs, const char *newrefname)
2587{
2588        struct strbuf path = STRBUF_INIT;
2589        struct strbuf tmp = STRBUF_INIT;
2590        struct rename_cb cb;
2591        int ret;
2592
2593        files_reflog_path(refs, &path, newrefname);
2594        files_reflog_path(refs, &tmp, TMP_RENAMED_LOG);
2595        cb.tmp_renamed_log = tmp.buf;
2596        ret = raceproof_create_file(path.buf, rename_tmp_log_callback, &cb);
2597        if (ret) {
2598                if (errno == EISDIR)
2599                        error("directory not empty: %s", path.buf);
2600                else
2601                        error("unable to move logfile %s to %s: %s",
2602                              tmp.buf, path.buf,
2603                              strerror(cb.true_errno));
2604        }
2605
2606        strbuf_release(&path);
2607        strbuf_release(&tmp);
2608        return ret;
2609}
2610
2611static int files_verify_refname_available(struct ref_store *ref_store,
2612                                          const char *newname,
2613                                          const struct string_list *extras,
2614                                          const struct string_list *skip,
2615                                          struct strbuf *err)
2616{
2617        struct files_ref_store *refs =
2618                files_downcast(ref_store, REF_STORE_READ, "verify_refname_available");
2619        struct ref_dir *packed_refs = get_packed_refs(refs);
2620        struct ref_dir *loose_refs = get_loose_refs(refs);
2621
2622        if (verify_refname_available_dir(newname, extras, skip,
2623                                         packed_refs, err) ||
2624            verify_refname_available_dir(newname, extras, skip,
2625                                         loose_refs, err))
2626                return -1;
2627
2628        return 0;
2629}
2630
2631static int write_ref_to_lockfile(struct ref_lock *lock,
2632                                 const unsigned char *sha1, struct strbuf *err);
2633static int commit_ref_update(struct files_ref_store *refs,
2634                             struct ref_lock *lock,
2635                             const unsigned char *sha1, const char *logmsg,
2636                             struct strbuf *err);
2637
2638static int files_rename_ref(struct ref_store *ref_store,
2639                            const char *oldrefname, const char *newrefname,
2640                            const char *logmsg)
2641{
2642        struct files_ref_store *refs =
2643                files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
2644        unsigned char sha1[20], orig_sha1[20];
2645        int flag = 0, logmoved = 0;
2646        struct ref_lock *lock;
2647        struct stat loginfo;
2648        struct strbuf sb_oldref = STRBUF_INIT;
2649        struct strbuf sb_newref = STRBUF_INIT;
2650        struct strbuf tmp_renamed_log = STRBUF_INIT;
2651        int log, ret;
2652        struct strbuf err = STRBUF_INIT;
2653
2654        files_reflog_path(refs, &sb_oldref, oldrefname);
2655        files_reflog_path(refs, &sb_newref, newrefname);
2656        files_reflog_path(refs, &tmp_renamed_log, TMP_RENAMED_LOG);
2657
2658        log = !lstat(sb_oldref.buf, &loginfo);
2659        if (log && S_ISLNK(loginfo.st_mode)) {
2660                ret = error("reflog for %s is a symlink", oldrefname);
2661                goto out;
2662        }
2663
2664        if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
2665                                     RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
2666                                orig_sha1, &flag)) {
2667                ret = error("refname %s not found", oldrefname);
2668                goto out;
2669        }
2670
2671        if (flag & REF_ISSYMREF) {
2672                ret = error("refname %s is a symbolic ref, renaming it is not supported",
2673                            oldrefname);
2674                goto out;
2675        }
2676        if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
2677                ret = 1;
2678                goto out;
2679        }
2680
2681        if (log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
2682                ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
2683                            oldrefname, strerror(errno));
2684                goto out;
2685        }
2686
2687        if (refs_delete_ref(&refs->base, logmsg, oldrefname,
2688                            orig_sha1, REF_NODEREF)) {
2689                error("unable to delete old %s", oldrefname);
2690                goto rollback;
2691        }
2692
2693        /*
2694         * Since we are doing a shallow lookup, sha1 is not the
2695         * correct value to pass to delete_ref as old_sha1. But that
2696         * doesn't matter, because an old_sha1 check wouldn't add to
2697         * the safety anyway; we want to delete the reference whatever
2698         * its current value.
2699         */
2700        if (!refs_read_ref_full(&refs->base, newrefname,
2701                                RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
2702                                sha1, NULL) &&
2703            refs_delete_ref(&refs->base, NULL, newrefname,
2704                            NULL, REF_NODEREF)) {
2705                if (errno == EISDIR) {
2706                        struct strbuf path = STRBUF_INIT;
2707                        int result;
2708
2709                        files_ref_path(refs, &path, newrefname);
2710                        result = remove_empty_directories(&path);
2711                        strbuf_release(&path);
2712
2713                        if (result) {
2714                                error("Directory not empty: %s", newrefname);
2715                                goto rollback;
2716                        }
2717                } else {
2718                        error("unable to delete existing %s", newrefname);
2719                        goto rollback;
2720                }
2721        }
2722
2723        if (log && rename_tmp_log(refs, newrefname))
2724                goto rollback;
2725
2726        logmoved = log;
2727
2728        lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
2729                                   REF_NODEREF, NULL, &err);
2730        if (!lock) {
2731                error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
2732                strbuf_release(&err);
2733                goto rollback;
2734        }
2735        hashcpy(lock->old_oid.hash, orig_sha1);
2736
2737        if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
2738            commit_ref_update(refs, lock, orig_sha1, logmsg, &err)) {
2739                error("unable to write current sha1 into %s: %s", newrefname, err.buf);
2740                strbuf_release(&err);
2741                goto rollback;
2742        }
2743
2744        ret = 0;
2745        goto out;
2746
2747 rollback:
2748        lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
2749                                   REF_NODEREF, NULL, &err);
2750        if (!lock) {
2751                error("unable to lock %s for rollback: %s", oldrefname, err.buf);
2752                strbuf_release(&err);
2753                goto rollbacklog;
2754        }
2755
2756        flag = log_all_ref_updates;
2757        log_all_ref_updates = LOG_REFS_NONE;
2758        if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
2759            commit_ref_update(refs, lock, orig_sha1, NULL, &err)) {
2760                error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
2761                strbuf_release(&err);
2762        }
2763        log_all_ref_updates = flag;
2764
2765 rollbacklog:
2766        if (logmoved && rename(sb_newref.buf, sb_oldref.buf))
2767                error("unable to restore logfile %s from %s: %s",
2768                        oldrefname, newrefname, strerror(errno));
2769        if (!logmoved && log &&
2770            rename(tmp_renamed_log.buf, sb_oldref.buf))
2771                error("unable to restore logfile %s from logs/"TMP_RENAMED_LOG": %s",
2772                        oldrefname, strerror(errno));
2773        ret = 1;
2774 out:
2775        strbuf_release(&sb_newref);
2776        strbuf_release(&sb_oldref);
2777        strbuf_release(&tmp_renamed_log);
2778
2779        return ret;
2780}
2781
2782static int close_ref(struct ref_lock *lock)
2783{
2784        if (close_lock_file(lock->lk))
2785                return -1;
2786        return 0;
2787}
2788
2789static int commit_ref(struct ref_lock *lock)
2790{
2791        char *path = get_locked_file_path(lock->lk);
2792        struct stat st;
2793
2794        if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
2795                /*
2796                 * There is a directory at the path we want to rename
2797                 * the lockfile to. Hopefully it is empty; try to
2798                 * delete it.
2799                 */
2800                size_t len = strlen(path);
2801                struct strbuf sb_path = STRBUF_INIT;
2802
2803                strbuf_attach(&sb_path, path, len, len);
2804
2805                /*
2806                 * If this fails, commit_lock_file() will also fail
2807                 * and will report the problem.
2808                 */
2809                remove_empty_directories(&sb_path);
2810                strbuf_release(&sb_path);
2811        } else {
2812                free(path);
2813        }
2814
2815        if (commit_lock_file(lock->lk))
2816                return -1;
2817        return 0;
2818}
2819
2820static int open_or_create_logfile(const char *path, void *cb)
2821{
2822        int *fd = cb;
2823
2824        *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
2825        return (*fd < 0) ? -1 : 0;
2826}
2827
2828/*
2829 * Create a reflog for a ref. If force_create = 0, only create the
2830 * reflog for certain refs (those for which should_autocreate_reflog
2831 * returns non-zero). Otherwise, create it regardless of the reference
2832 * name. If the logfile already existed or was created, return 0 and
2833 * set *logfd to the file descriptor opened for appending to the file.
2834 * If no logfile exists and we decided not to create one, return 0 and
2835 * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
2836 * return -1.
2837 */
2838static int log_ref_setup(struct files_ref_store *refs,
2839                         const char *refname, int force_create,
2840                         int *logfd, struct strbuf *err)
2841{
2842        struct strbuf logfile_sb = STRBUF_INIT;
2843        char *logfile;
2844
2845        files_reflog_path(refs, &logfile_sb, refname);
2846        logfile = strbuf_detach(&logfile_sb, NULL);
2847
2848        if (force_create || should_autocreate_reflog(refname)) {
2849                if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
2850                        if (errno == ENOENT)
2851                                strbuf_addf(err, "unable to create directory for '%s': "
2852                                            "%s", logfile, strerror(errno));
2853                        else if (errno == EISDIR)
2854                                strbuf_addf(err, "there are still logs under '%s'",
2855                                            logfile);
2856                        else
2857                                strbuf_addf(err, "unable to append to '%s': %s",
2858                                            logfile, strerror(errno));
2859
2860                        goto error;
2861                }
2862        } else {
2863                *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
2864                if (*logfd < 0) {
2865                        if (errno == ENOENT || errno == EISDIR) {
2866                                /*
2867                                 * The logfile doesn't already exist,
2868                                 * but that is not an error; it only
2869                                 * means that we won't write log
2870                                 * entries to it.
2871                                 */
2872                                ;
2873                        } else {
2874                                strbuf_addf(err, "unable to append to '%s': %s",
2875                                            logfile, strerror(errno));
2876                                goto error;
2877                        }
2878                }
2879        }
2880
2881        if (*logfd >= 0)
2882                adjust_shared_perm(logfile);
2883
2884        free(logfile);
2885        return 0;
2886
2887error:
2888        free(logfile);
2889        return -1;
2890}
2891
2892static int files_create_reflog(struct ref_store *ref_store,
2893                               const char *refname, int force_create,
2894                               struct strbuf *err)
2895{
2896        struct files_ref_store *refs =
2897                files_downcast(ref_store, REF_STORE_WRITE, "create_reflog");
2898        int fd;
2899
2900        if (log_ref_setup(refs, refname, force_create, &fd, err))
2901                return -1;
2902
2903        if (fd >= 0)
2904                close(fd);
2905
2906        return 0;
2907}
2908
2909static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
2910                            const unsigned char *new_sha1,
2911                            const char *committer, const char *msg)
2912{
2913        int msglen, written;
2914        unsigned maxlen, len;
2915        char *logrec;
2916
2917        msglen = msg ? strlen(msg) : 0;
2918        maxlen = strlen(committer) + msglen + 100;
2919        logrec = xmalloc(maxlen);
2920        len = xsnprintf(logrec, maxlen, "%s %s %s\n",
2921                        sha1_to_hex(old_sha1),
2922                        sha1_to_hex(new_sha1),
2923                        committer);
2924        if (msglen)
2925                len += copy_reflog_msg(logrec + len - 1, msg) - 1;
2926
2927        written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
2928        free(logrec);
2929        if (written != len)
2930                return -1;
2931
2932        return 0;
2933}
2934
2935static int files_log_ref_write(struct files_ref_store *refs,
2936                               const char *refname, const unsigned char *old_sha1,
2937                               const unsigned char *new_sha1, const char *msg,
2938                               int flags, struct strbuf *err)
2939{
2940        int logfd, result;
2941
2942        if (log_all_ref_updates == LOG_REFS_UNSET)
2943                log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
2944
2945        result = log_ref_setup(refs, refname,
2946                               flags & REF_FORCE_CREATE_REFLOG,
2947                               &logfd, err);
2948
2949        if (result)
2950                return result;
2951
2952        if (logfd < 0)
2953                return 0;
2954        result = log_ref_write_fd(logfd, old_sha1, new_sha1,
2955                                  git_committer_info(0), msg);
2956        if (result) {
2957                struct strbuf sb = STRBUF_INIT;
2958                int save_errno = errno;
2959
2960                files_reflog_path(refs, &sb, refname);
2961                strbuf_addf(err, "unable to append to '%s': %s",
2962                            sb.buf, strerror(save_errno));
2963                strbuf_release(&sb);
2964                close(logfd);
2965                return -1;
2966        }
2967        if (close(logfd)) {
2968                struct strbuf sb = STRBUF_INIT;
2969                int save_errno = errno;
2970
2971                files_reflog_path(refs, &sb, refname);
2972                strbuf_addf(err, "unable to append to '%s': %s",
2973                            sb.buf, strerror(save_errno));
2974                strbuf_release(&sb);
2975                return -1;
2976        }
2977        return 0;
2978}
2979
2980/*
2981 * Write sha1 into the open lockfile, then close the lockfile. On
2982 * errors, rollback the lockfile, fill in *err and
2983 * return -1.
2984 */
2985static int write_ref_to_lockfile(struct ref_lock *lock,
2986                                 const unsigned char *sha1, struct strbuf *err)
2987{
2988        static char term = '\n';
2989        struct object *o;
2990        int fd;
2991
2992        o = parse_object(sha1);
2993        if (!o) {
2994                strbuf_addf(err,
2995                            "trying to write ref '%s' with nonexistent object %s",
2996                            lock->ref_name, sha1_to_hex(sha1));
2997                unlock_ref(lock);
2998                return -1;
2999        }
3000        if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
3001                strbuf_addf(err,
3002                            "trying to write non-commit object %s to branch '%s'",
3003                            sha1_to_hex(sha1), lock->ref_name);
3004                unlock_ref(lock);
3005                return -1;
3006        }
3007        fd = get_lock_file_fd(lock->lk);
3008        if (write_in_full(fd, sha1_to_hex(sha1), 40) != 40 ||
3009            write_in_full(fd, &term, 1) != 1 ||
3010            close_ref(lock) < 0) {
3011                strbuf_addf(err,
3012                            "couldn't write '%s'", get_lock_file_path(lock->lk));
3013                unlock_ref(lock);
3014                return -1;
3015        }
3016        return 0;
3017}
3018
3019/*
3020 * Commit a change to a loose reference that has already been written
3021 * to the loose reference lockfile. Also update the reflogs if
3022 * necessary, using the specified lockmsg (which can be NULL).
3023 */
3024static int commit_ref_update(struct files_ref_store *refs,
3025                             struct ref_lock *lock,
3026                             const unsigned char *sha1, const char *logmsg,
3027                             struct strbuf *err)
3028{
3029        files_assert_main_repository(refs, "commit_ref_update");
3030
3031        clear_loose_ref_cache(refs);
3032        if (files_log_ref_write(refs, lock->ref_name,
3033                                lock->old_oid.hash, sha1,
3034                                logmsg, 0, err)) {
3035                char *old_msg = strbuf_detach(err, NULL);
3036                strbuf_addf(err, "cannot update the ref '%s': %s",
3037                            lock->ref_name, old_msg);
3038                free(old_msg);
3039                unlock_ref(lock);
3040                return -1;
3041        }
3042
3043        if (strcmp(lock->ref_name, "HEAD") != 0) {
3044                /*
3045                 * Special hack: If a branch is updated directly and HEAD
3046                 * points to it (may happen on the remote side of a push
3047                 * for example) then logically the HEAD reflog should be
3048                 * updated too.
3049                 * A generic solution implies reverse symref information,
3050                 * but finding all symrefs pointing to the given branch
3051                 * would be rather costly for this rare event (the direct
3052                 * update of a branch) to be worth it.  So let's cheat and
3053                 * check with HEAD only which should cover 99% of all usage
3054                 * scenarios (even 100% of the default ones).
3055                 */
3056                unsigned char head_sha1[20];
3057                int head_flag;
3058                const char *head_ref;
3059
3060                head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
3061                                                   RESOLVE_REF_READING,
3062                                                   head_sha1, &head_flag);
3063                if (head_ref && (head_flag & REF_ISSYMREF) &&
3064                    !strcmp(head_ref, lock->ref_name)) {
3065                        struct strbuf log_err = STRBUF_INIT;
3066                        if (files_log_ref_write(refs, "HEAD",
3067                                                lock->old_oid.hash, sha1,
3068                                                logmsg, 0, &log_err)) {
3069                                error("%s", log_err.buf);
3070                                strbuf_release(&log_err);
3071                        }
3072                }
3073        }
3074
3075        if (commit_ref(lock)) {
3076                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
3077                unlock_ref(lock);
3078                return -1;
3079        }
3080
3081        unlock_ref(lock);
3082        return 0;
3083}
3084
3085static int create_ref_symlink(struct ref_lock *lock, const char *target)
3086{
3087        int ret = -1;
3088#ifndef NO_SYMLINK_HEAD
3089        char *ref_path = get_locked_file_path(lock->lk);
3090        unlink(ref_path);
3091        ret = symlink(target, ref_path);
3092        free(ref_path);
3093
3094        if (ret)
3095                fprintf(stderr, "no symlink - falling back to symbolic ref\n");
3096#endif
3097        return ret;
3098}
3099
3100static void update_symref_reflog(struct files_ref_store *refs,
3101                                 struct ref_lock *lock, const char *refname,
3102                                 const char *target, const char *logmsg)
3103{
3104        struct strbuf err = STRBUF_INIT;
3105        unsigned char new_sha1[20];
3106        if (logmsg &&
3107            !refs_read_ref_full(&refs->base, target,
3108                                RESOLVE_REF_READING, new_sha1, NULL) &&
3109            files_log_ref_write(refs, refname, lock->old_oid.hash,
3110                                new_sha1, logmsg, 0, &err)) {
3111                error("%s", err.buf);
3112                strbuf_release(&err);
3113        }
3114}
3115
3116static int create_symref_locked(struct files_ref_store *refs,
3117                                struct ref_lock *lock, const char *refname,
3118                                const char *target, const char *logmsg)
3119{
3120        if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
3121                update_symref_reflog(refs, lock, refname, target, logmsg);
3122                return 0;
3123        }
3124
3125        if (!fdopen_lock_file(lock->lk, "w"))
3126                return error("unable to fdopen %s: %s",
3127                             lock->lk->tempfile.filename.buf, strerror(errno));
3128
3129        update_symref_reflog(refs, lock, refname, target, logmsg);
3130
3131        /* no error check; commit_ref will check ferror */
3132        fprintf(lock->lk->tempfile.fp, "ref: %s\n", target);
3133        if (commit_ref(lock) < 0)
3134                return error("unable to write symref for %s: %s", refname,
3135                             strerror(errno));
3136        return 0;
3137}
3138
3139static int files_create_symref(struct ref_store *ref_store,
3140                               const char *refname, const char *target,
3141                               const char *logmsg)
3142{
3143        struct files_ref_store *refs =
3144                files_downcast(ref_store, REF_STORE_WRITE, "create_symref");
3145        struct strbuf err = STRBUF_INIT;
3146        struct ref_lock *lock;
3147        int ret;
3148
3149        lock = lock_ref_sha1_basic(refs, refname, NULL,
3150                                   NULL, NULL, REF_NODEREF, NULL,
3151                                   &err);
3152        if (!lock) {
3153                error("%s", err.buf);
3154                strbuf_release(&err);
3155                return -1;
3156        }
3157
3158        ret = create_symref_locked(refs, lock, refname, target, logmsg);
3159        unlock_ref(lock);
3160        return ret;
3161}
3162
3163int set_worktree_head_symref(const char *gitdir, const char *target, const char *logmsg)
3164{
3165        /*
3166         * FIXME: this obviously will not work well for future refs
3167         * backends. This function needs to die.
3168         */
3169        struct files_ref_store *refs =
3170                files_downcast(get_main_ref_store(),
3171                               REF_STORE_WRITE,
3172                               "set_head_symref");
3173
3174        static struct lock_file head_lock;
3175        struct ref_lock *lock;
3176        struct strbuf head_path = STRBUF_INIT;
3177        const char *head_rel;
3178        int ret;
3179
3180        strbuf_addf(&head_path, "%s/HEAD", absolute_path(gitdir));
3181        if (hold_lock_file_for_update(&head_lock, head_path.buf,
3182                                      LOCK_NO_DEREF) < 0) {
3183                struct strbuf err = STRBUF_INIT;
3184                unable_to_lock_message(head_path.buf, errno, &err);
3185                error("%s", err.buf);
3186                strbuf_release(&err);
3187                strbuf_release(&head_path);
3188                return -1;
3189        }
3190
3191        /* head_rel will be "HEAD" for the main tree, "worktrees/wt/HEAD" for
3192           linked trees */
3193        head_rel = remove_leading_path(head_path.buf,
3194                                       absolute_path(get_git_common_dir()));
3195        /* to make use of create_symref_locked(), initialize ref_lock */
3196        lock = xcalloc(1, sizeof(struct ref_lock));
3197        lock->lk = &head_lock;
3198        lock->ref_name = xstrdup(head_rel);
3199
3200        ret = create_symref_locked(refs, lock, head_rel, target, logmsg);
3201
3202        unlock_ref(lock); /* will free lock */
3203        strbuf_release(&head_path);
3204        return ret;
3205}
3206
3207static int files_reflog_exists(struct ref_store *ref_store,
3208                               const char *refname)
3209{
3210        struct files_ref_store *refs =
3211                files_downcast(ref_store, REF_STORE_READ, "reflog_exists");
3212        struct strbuf sb = STRBUF_INIT;
3213        struct stat st;
3214        int ret;
3215
3216        files_reflog_path(refs, &sb, refname);
3217        ret = !lstat(sb.buf, &st) && S_ISREG(st.st_mode);
3218        strbuf_release(&sb);
3219        return ret;
3220}
3221
3222static int files_delete_reflog(struct ref_store *ref_store,
3223                               const char *refname)
3224{
3225        struct files_ref_store *refs =
3226                files_downcast(ref_store, REF_STORE_WRITE, "delete_reflog");
3227        struct strbuf sb = STRBUF_INIT;
3228        int ret;
3229
3230        files_reflog_path(refs, &sb, refname);
3231        ret = remove_path(sb.buf);
3232        strbuf_release(&sb);
3233        return ret;
3234}
3235
3236static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
3237{
3238        struct object_id ooid, noid;
3239        char *email_end, *message;
3240        unsigned long timestamp;
3241        int tz;
3242        const char *p = sb->buf;
3243
3244        /* old SP new SP name <email> SP time TAB msg LF */
3245        if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
3246            parse_oid_hex(p, &ooid, &p) || *p++ != ' ' ||
3247            parse_oid_hex(p, &noid, &p) || *p++ != ' ' ||
3248            !(email_end = strchr(p, '>')) ||
3249            email_end[1] != ' ' ||
3250            !(timestamp = strtoul(email_end + 2, &message, 10)) ||
3251            !message || message[0] != ' ' ||
3252            (message[1] != '+' && message[1] != '-') ||
3253            !isdigit(message[2]) || !isdigit(message[3]) ||
3254            !isdigit(message[4]) || !isdigit(message[5]))
3255                return 0; /* corrupt? */
3256        email_end[1] = '\0';
3257        tz = strtol(message + 1, NULL, 10);
3258        if (message[6] != '\t')
3259                message += 6;
3260        else
3261                message += 7;
3262        return fn(&ooid, &noid, p, timestamp, tz, message, cb_data);
3263}
3264
3265static char *find_beginning_of_line(char *bob, char *scan)
3266{
3267        while (bob < scan && *(--scan) != '\n')
3268                ; /* keep scanning backwards */
3269        /*
3270         * Return either beginning of the buffer, or LF at the end of
3271         * the previous line.
3272         */
3273        return scan;
3274}
3275
3276static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
3277                                             const char *refname,
3278                                             each_reflog_ent_fn fn,
3279                                             void *cb_data)
3280{
3281        struct files_ref_store *refs =
3282                files_downcast(ref_store, REF_STORE_READ,
3283                               "for_each_reflog_ent_reverse");
3284        struct strbuf sb = STRBUF_INIT;
3285        FILE *logfp;
3286        long pos;
3287        int ret = 0, at_tail = 1;
3288
3289        files_reflog_path(refs, &sb, refname);
3290        logfp = fopen(sb.buf, "r");
3291        strbuf_release(&sb);
3292        if (!logfp)
3293                return -1;
3294
3295        /* Jump to the end */
3296        if (fseek(logfp, 0, SEEK_END) < 0)
3297                return error("cannot seek back reflog for %s: %s",
3298                             refname, strerror(errno));
3299        pos = ftell(logfp);
3300        while (!ret && 0 < pos) {
3301                int cnt;
3302                size_t nread;
3303                char buf[BUFSIZ];
3304                char *endp, *scanp;
3305
3306                /* Fill next block from the end */
3307                cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
3308                if (fseek(logfp, pos - cnt, SEEK_SET))
3309                        return error("cannot seek back reflog for %s: %s",
3310                                     refname, strerror(errno));
3311                nread = fread(buf, cnt, 1, logfp);
3312                if (nread != 1)
3313                        return error("cannot read %d bytes from reflog for %s: %s",
3314                                     cnt, refname, strerror(errno));
3315                pos -= cnt;
3316
3317                scanp = endp = buf + cnt;
3318                if (at_tail && scanp[-1] == '\n')
3319                        /* Looking at the final LF at the end of the file */
3320                        scanp--;
3321                at_tail = 0;
3322
3323                while (buf < scanp) {
3324                        /*
3325                         * terminating LF of the previous line, or the beginning
3326                         * of the buffer.
3327                         */
3328                        char *bp;
3329
3330                        bp = find_beginning_of_line(buf, scanp);
3331
3332                        if (*bp == '\n') {
3333                                /*
3334                                 * The newline is the end of the previous line,
3335                                 * so we know we have complete line starting
3336                                 * at (bp + 1). Prefix it onto any prior data
3337                                 * we collected for the line and process it.
3338                                 */
3339                                strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
3340                                scanp = bp;
3341                                endp = bp + 1;
3342                                ret = show_one_reflog_ent(&sb, fn, cb_data);
3343                                strbuf_reset(&sb);
3344                                if (ret)
3345                                        break;
3346                        } else if (!pos) {
3347                                /*
3348                                 * We are at the start of the buffer, and the
3349                                 * start of the file; there is no previous
3350                                 * line, and we have everything for this one.
3351                                 * Process it, and we can end the loop.
3352                                 */
3353                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
3354                                ret = show_one_reflog_ent(&sb, fn, cb_data);
3355                                strbuf_reset(&sb);
3356                                break;
3357                        }
3358
3359                        if (bp == buf) {
3360                                /*
3361                                 * We are at the start of the buffer, and there
3362                                 * is more file to read backwards. Which means
3363                                 * we are in the middle of a line. Note that we
3364                                 * may get here even if *bp was a newline; that
3365                                 * just means we are at the exact end of the
3366                                 * previous line, rather than some spot in the
3367                                 * middle.
3368                                 *
3369                                 * Save away what we have to be combined with
3370                                 * the data from the next read.
3371                                 */
3372                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
3373                                break;
3374                        }
3375                }
3376
3377        }
3378        if (!ret && sb.len)
3379                die("BUG: reverse reflog parser had leftover data");
3380
3381        fclose(logfp);
3382        strbuf_release(&sb);
3383        return ret;
3384}
3385
3386static int files_for_each_reflog_ent(struct ref_store *ref_store,
3387                                     const char *refname,
3388                                     each_reflog_ent_fn fn, void *cb_data)
3389{
3390        struct files_ref_store *refs =
3391                files_downcast(ref_store, REF_STORE_READ,
3392                               "for_each_reflog_ent");
3393        FILE *logfp;
3394        struct strbuf sb = STRBUF_INIT;
3395        int ret = 0;
3396
3397        files_reflog_path(refs, &sb, refname);
3398        logfp = fopen(sb.buf, "r");
3399        strbuf_release(&sb);
3400        if (!logfp)
3401                return -1;
3402
3403        while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
3404                ret = show_one_reflog_ent(&sb, fn, cb_data);
3405        fclose(logfp);
3406        strbuf_release(&sb);
3407        return ret;
3408}
3409
3410struct files_reflog_iterator {
3411        struct ref_iterator base;
3412
3413        struct ref_store *ref_store;
3414        struct dir_iterator *dir_iterator;
3415        struct object_id oid;
3416};
3417
3418static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
3419{
3420        struct files_reflog_iterator *iter =
3421                (struct files_reflog_iterator *)ref_iterator;
3422        struct dir_iterator *diter = iter->dir_iterator;
3423        int ok;
3424
3425        while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
3426                int flags;
3427
3428                if (!S_ISREG(diter->st.st_mode))
3429                        continue;
3430                if (diter->basename[0] == '.')
3431                        continue;
3432                if (ends_with(diter->basename, ".lock"))
3433                        continue;
3434
3435                if (refs_read_ref_full(iter->ref_store,
3436                                       diter->relative_path, 0,
3437                                       iter->oid.hash, &flags)) {
3438                        error("bad ref for %s", diter->path.buf);
3439                        continue;
3440                }
3441
3442                iter->base.refname = diter->relative_path;
3443                iter->base.oid = &iter->oid;
3444                iter->base.flags = flags;
3445                return ITER_OK;
3446        }
3447
3448        iter->dir_iterator = NULL;
3449        if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
3450                ok = ITER_ERROR;
3451        return ok;
3452}
3453
3454static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
3455                                   struct object_id *peeled)
3456{
3457        die("BUG: ref_iterator_peel() called for reflog_iterator");
3458}
3459
3460static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
3461{
3462        struct files_reflog_iterator *iter =
3463                (struct files_reflog_iterator *)ref_iterator;
3464        int ok = ITER_DONE;
3465
3466        if (iter->dir_iterator)
3467                ok = dir_iterator_abort(iter->dir_iterator);
3468
3469        base_ref_iterator_free(ref_iterator);
3470        return ok;
3471}
3472
3473static struct ref_iterator_vtable files_reflog_iterator_vtable = {
3474        files_reflog_iterator_advance,
3475        files_reflog_iterator_peel,
3476        files_reflog_iterator_abort
3477};
3478
3479static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
3480{
3481        struct files_ref_store *refs =
3482                files_downcast(ref_store, REF_STORE_READ,
3483                               "reflog_iterator_begin");
3484        struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
3485        struct ref_iterator *ref_iterator = &iter->base;
3486        struct strbuf sb = STRBUF_INIT;
3487
3488        base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
3489        files_reflog_path(refs, &sb, NULL);
3490        iter->dir_iterator = dir_iterator_begin(sb.buf);
3491        iter->ref_store = ref_store;
3492        strbuf_release(&sb);
3493        return ref_iterator;
3494}
3495
3496static int ref_update_reject_duplicates(struct string_list *refnames,
3497                                        struct strbuf *err)
3498{
3499        int i, n = refnames->nr;
3500
3501        assert(err);
3502
3503        for (i = 1; i < n; i++)
3504                if (!strcmp(refnames->items[i - 1].string, refnames->items[i].string)) {
3505                        strbuf_addf(err,
3506                                    "multiple updates for ref '%s' not allowed.",
3507                                    refnames->items[i].string);
3508                        return 1;
3509                }
3510        return 0;
3511}
3512
3513/*
3514 * If update is a direct update of head_ref (the reference pointed to
3515 * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
3516 */
3517static int split_head_update(struct ref_update *update,
3518                             struct ref_transaction *transaction,
3519                             const char *head_ref,
3520                             struct string_list *affected_refnames,
3521                             struct strbuf *err)
3522{
3523        struct string_list_item *item;
3524        struct ref_update *new_update;
3525
3526        if ((update->flags & REF_LOG_ONLY) ||
3527            (update->flags & REF_ISPRUNING) ||
3528            (update->flags & REF_UPDATE_VIA_HEAD))
3529                return 0;
3530
3531        if (strcmp(update->refname, head_ref))
3532                return 0;
3533
3534        /*
3535         * First make sure that HEAD is not already in the
3536         * transaction. This insertion is O(N) in the transaction
3537         * size, but it happens at most once per transaction.
3538         */
3539        item = string_list_insert(affected_refnames, "HEAD");
3540        if (item->util) {
3541                /* An entry already existed */
3542                strbuf_addf(err,
3543                            "multiple updates for 'HEAD' (including one "
3544                            "via its referent '%s') are not allowed",
3545                            update->refname);
3546                return TRANSACTION_NAME_CONFLICT;
3547        }
3548
3549        new_update = ref_transaction_add_update(
3550                        transaction, "HEAD",
3551                        update->flags | REF_LOG_ONLY | REF_NODEREF,
3552                        update->new_sha1, update->old_sha1,
3553                        update->msg);
3554
3555        item->util = new_update;
3556
3557        return 0;
3558}
3559
3560/*
3561 * update is for a symref that points at referent and doesn't have
3562 * REF_NODEREF set. Split it into two updates:
3563 * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
3564 * - A new, separate update for the referent reference
3565 * Note that the new update will itself be subject to splitting when
3566 * the iteration gets to it.
3567 */
3568static int split_symref_update(struct files_ref_store *refs,
3569                               struct ref_update *update,
3570                               const char *referent,
3571                               struct ref_transaction *transaction,
3572                               struct string_list *affected_refnames,
3573                               struct strbuf *err)
3574{
3575        struct string_list_item *item;
3576        struct ref_update *new_update;
3577        unsigned int new_flags;
3578
3579        /*
3580         * First make sure that referent is not already in the
3581         * transaction. This insertion is O(N) in the transaction
3582         * size, but it happens at most once per symref in a
3583         * transaction.
3584         */
3585        item = string_list_insert(affected_refnames, referent);
3586        if (item->util) {
3587                /* An entry already existed */
3588                strbuf_addf(err,
3589                            "multiple updates for '%s' (including one "
3590                            "via symref '%s') are not allowed",
3591                            referent, update->refname);
3592                return TRANSACTION_NAME_CONFLICT;
3593        }
3594
3595        new_flags = update->flags;
3596        if (!strcmp(update->refname, "HEAD")) {
3597                /*
3598                 * Record that the new update came via HEAD, so that
3599                 * when we process it, split_head_update() doesn't try
3600                 * to add another reflog update for HEAD. Note that
3601                 * this bit will be propagated if the new_update
3602                 * itself needs to be split.
3603                 */
3604                new_flags |= REF_UPDATE_VIA_HEAD;
3605        }
3606
3607        new_update = ref_transaction_add_update(
3608                        transaction, referent, new_flags,
3609                        update->new_sha1, update->old_sha1,
3610                        update->msg);
3611
3612        new_update->parent_update = update;
3613
3614        /*
3615         * Change the symbolic ref update to log only. Also, it
3616         * doesn't need to check its old SHA-1 value, as that will be
3617         * done when new_update is processed.
3618         */
3619        update->flags |= REF_LOG_ONLY | REF_NODEREF;
3620        update->flags &= ~REF_HAVE_OLD;
3621
3622        item->util = new_update;
3623
3624        return 0;
3625}
3626
3627/*
3628 * Return the refname under which update was originally requested.
3629 */
3630static const char *original_update_refname(struct ref_update *update)
3631{
3632        while (update->parent_update)
3633                update = update->parent_update;
3634
3635        return update->refname;
3636}
3637
3638/*
3639 * Check whether the REF_HAVE_OLD and old_oid values stored in update
3640 * are consistent with oid, which is the reference's current value. If
3641 * everything is OK, return 0; otherwise, write an error message to
3642 * err and return -1.
3643 */
3644static int check_old_oid(struct ref_update *update, struct object_id *oid,
3645                         struct strbuf *err)
3646{
3647        if (!(update->flags & REF_HAVE_OLD) ||
3648                   !hashcmp(oid->hash, update->old_sha1))
3649                return 0;
3650
3651        if (is_null_sha1(update->old_sha1))
3652                strbuf_addf(err, "cannot lock ref '%s': "
3653                            "reference already exists",
3654                            original_update_refname(update));
3655        else if (is_null_oid(oid))
3656                strbuf_addf(err, "cannot lock ref '%s': "
3657                            "reference is missing but expected %s",
3658                            original_update_refname(update),
3659                            sha1_to_hex(update->old_sha1));
3660        else
3661                strbuf_addf(err, "cannot lock ref '%s': "
3662                            "is at %s but expected %s",
3663                            original_update_refname(update),
3664                            oid_to_hex(oid),
3665                            sha1_to_hex(update->old_sha1));
3666
3667        return -1;
3668}
3669
3670/*
3671 * Prepare for carrying out update:
3672 * - Lock the reference referred to by update.
3673 * - Read the reference under lock.
3674 * - Check that its old SHA-1 value (if specified) is correct, and in
3675 *   any case record it in update->lock->old_oid for later use when
3676 *   writing the reflog.
3677 * - If it is a symref update without REF_NODEREF, split it up into a
3678 *   REF_LOG_ONLY update of the symref and add a separate update for
3679 *   the referent to transaction.
3680 * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
3681 *   update of HEAD.
3682 */
3683static int lock_ref_for_update(struct files_ref_store *refs,
3684                               struct ref_update *update,
3685                               struct ref_transaction *transaction,
3686                               const char *head_ref,
3687                               struct string_list *affected_refnames,
3688                               struct strbuf *err)
3689{
3690        struct strbuf referent = STRBUF_INIT;
3691        int mustexist = (update->flags & REF_HAVE_OLD) &&
3692                !is_null_sha1(update->old_sha1);
3693        int ret;
3694        struct ref_lock *lock;
3695
3696        files_assert_main_repository(refs, "lock_ref_for_update");
3697
3698        if ((update->flags & REF_HAVE_NEW) && is_null_sha1(update->new_sha1))
3699                update->flags |= REF_DELETING;
3700
3701        if (head_ref) {
3702                ret = split_head_update(update, transaction, head_ref,
3703                                        affected_refnames, err);
3704                if (ret)
3705                        return ret;
3706        }
3707
3708        ret = lock_raw_ref(refs, update->refname, mustexist,
3709                           affected_refnames, NULL,
3710                           &lock, &referent,
3711                           &update->type, err);
3712        if (ret) {
3713                char *reason;
3714
3715                reason = strbuf_detach(err, NULL);
3716                strbuf_addf(err, "cannot lock ref '%s': %s",
3717                            original_update_refname(update), reason);
3718                free(reason);
3719                return ret;
3720        }
3721
3722        update->backend_data = lock;
3723
3724        if (update->type & REF_ISSYMREF) {
3725                if (update->flags & REF_NODEREF) {
3726                        /*
3727                         * We won't be reading the referent as part of
3728                         * the transaction, so we have to read it here
3729                         * to record and possibly check old_sha1:
3730                         */
3731                        if (refs_read_ref_full(&refs->base,
3732                                               referent.buf, 0,
3733                                               lock->old_oid.hash, NULL)) {
3734                                if (update->flags & REF_HAVE_OLD) {
3735                                        strbuf_addf(err, "cannot lock ref '%s': "
3736                                                    "error reading reference",
3737                                                    original_update_refname(update));
3738                                        return -1;
3739                                }
3740                        } else if (check_old_oid(update, &lock->old_oid, err)) {
3741                                return TRANSACTION_GENERIC_ERROR;
3742                        }
3743                } else {
3744                        /*
3745                         * Create a new update for the reference this
3746                         * symref is pointing at. Also, we will record
3747                         * and verify old_sha1 for this update as part
3748                         * of processing the split-off update, so we
3749                         * don't have to do it here.
3750                         */
3751                        ret = split_symref_update(refs, update,
3752                                                  referent.buf, transaction,
3753                                                  affected_refnames, err);
3754                        if (ret)
3755                                return ret;
3756                }
3757        } else {
3758                struct ref_update *parent_update;
3759
3760                if (check_old_oid(update, &lock->old_oid, err))
3761                        return TRANSACTION_GENERIC_ERROR;
3762
3763                /*
3764                 * If this update is happening indirectly because of a
3765                 * symref update, record the old SHA-1 in the parent
3766                 * update:
3767                 */
3768                for (parent_update = update->parent_update;
3769                     parent_update;
3770                     parent_update = parent_update->parent_update) {
3771                        struct ref_lock *parent_lock = parent_update->backend_data;
3772                        oidcpy(&parent_lock->old_oid, &lock->old_oid);
3773                }
3774        }
3775
3776        if ((update->flags & REF_HAVE_NEW) &&
3777            !(update->flags & REF_DELETING) &&
3778            !(update->flags & REF_LOG_ONLY)) {
3779                if (!(update->type & REF_ISSYMREF) &&
3780                    !hashcmp(lock->old_oid.hash, update->new_sha1)) {
3781                        /*
3782                         * The reference already has the desired
3783                         * value, so we don't need to write it.
3784                         */
3785                } else if (write_ref_to_lockfile(lock, update->new_sha1,
3786                                                 err)) {
3787                        char *write_err = strbuf_detach(err, NULL);
3788
3789                        /*
3790                         * The lock was freed upon failure of
3791                         * write_ref_to_lockfile():
3792                         */
3793                        update->backend_data = NULL;
3794                        strbuf_addf(err,
3795                                    "cannot update ref '%s': %s",
3796                                    update->refname, write_err);
3797                        free(write_err);
3798                        return TRANSACTION_GENERIC_ERROR;
3799                } else {
3800                        update->flags |= REF_NEEDS_COMMIT;
3801                }
3802        }
3803        if (!(update->flags & REF_NEEDS_COMMIT)) {
3804                /*
3805                 * We didn't call write_ref_to_lockfile(), so
3806                 * the lockfile is still open. Close it to
3807                 * free up the file descriptor:
3808                 */
3809                if (close_ref(lock)) {
3810                        strbuf_addf(err, "couldn't close '%s.lock'",
3811                                    update->refname);
3812                        return TRANSACTION_GENERIC_ERROR;
3813                }
3814        }
3815        return 0;
3816}
3817
3818static int files_transaction_commit(struct ref_store *ref_store,
3819                                    struct ref_transaction *transaction,
3820                                    struct strbuf *err)
3821{
3822        struct files_ref_store *refs =
3823                files_downcast(ref_store, REF_STORE_WRITE,
3824                               "ref_transaction_commit");
3825        int ret = 0, i;
3826        struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
3827        struct string_list_item *ref_to_delete;
3828        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
3829        char *head_ref = NULL;
3830        int head_type;
3831        struct object_id head_oid;
3832        struct strbuf sb = STRBUF_INIT;
3833
3834        assert(err);
3835
3836        if (transaction->state != REF_TRANSACTION_OPEN)
3837                die("BUG: commit called for transaction that is not open");
3838
3839        if (!transaction->nr) {
3840                transaction->state = REF_TRANSACTION_CLOSED;
3841                return 0;
3842        }
3843
3844        /*
3845         * Fail if a refname appears more than once in the
3846         * transaction. (If we end up splitting up any updates using
3847         * split_symref_update() or split_head_update(), those
3848         * functions will check that the new updates don't have the
3849         * same refname as any existing ones.)
3850         */
3851        for (i = 0; i < transaction->nr; i++) {
3852                struct ref_update *update = transaction->updates[i];
3853                struct string_list_item *item =
3854                        string_list_append(&affected_refnames, update->refname);
3855
3856                /*
3857                 * We store a pointer to update in item->util, but at
3858                 * the moment we never use the value of this field
3859                 * except to check whether it is non-NULL.
3860                 */
3861                item->util = update;
3862        }
3863        string_list_sort(&affected_refnames);
3864        if (ref_update_reject_duplicates(&affected_refnames, err)) {
3865                ret = TRANSACTION_GENERIC_ERROR;
3866                goto cleanup;
3867        }
3868
3869        /*
3870         * Special hack: If a branch is updated directly and HEAD
3871         * points to it (may happen on the remote side of a push
3872         * for example) then logically the HEAD reflog should be
3873         * updated too.
3874         *
3875         * A generic solution would require reverse symref lookups,
3876         * but finding all symrefs pointing to a given branch would be
3877         * rather costly for this rare event (the direct update of a
3878         * branch) to be worth it. So let's cheat and check with HEAD
3879         * only, which should cover 99% of all usage scenarios (even
3880         * 100% of the default ones).
3881         *
3882         * So if HEAD is a symbolic reference, then record the name of
3883         * the reference that it points to. If we see an update of
3884         * head_ref within the transaction, then split_head_update()
3885         * arranges for the reflog of HEAD to be updated, too.
3886         */
3887        head_ref = refs_resolve_refdup(ref_store, "HEAD",
3888                                       RESOLVE_REF_NO_RECURSE,
3889                                       head_oid.hash, &head_type);
3890
3891        if (head_ref && !(head_type & REF_ISSYMREF)) {
3892                free(head_ref);
3893                head_ref = NULL;
3894        }
3895
3896        /*
3897         * Acquire all locks, verify old values if provided, check
3898         * that new values are valid, and write new values to the
3899         * lockfiles, ready to be activated. Only keep one lockfile
3900         * open at a time to avoid running out of file descriptors.
3901         */
3902        for (i = 0; i < transaction->nr; i++) {
3903                struct ref_update *update = transaction->updates[i];
3904
3905                ret = lock_ref_for_update(refs, update, transaction,
3906                                          head_ref, &affected_refnames, err);
3907                if (ret)
3908                        goto cleanup;
3909        }
3910
3911        /* Perform updates first so live commits remain referenced */
3912        for (i = 0; i < transaction->nr; i++) {
3913                struct ref_update *update = transaction->updates[i];
3914                struct ref_lock *lock = update->backend_data;
3915
3916                if (update->flags & REF_NEEDS_COMMIT ||
3917                    update->flags & REF_LOG_ONLY) {
3918                        if (files_log_ref_write(refs,
3919                                                lock->ref_name,
3920                                                lock->old_oid.hash,
3921                                                update->new_sha1,
3922                                                update->msg, update->flags,
3923                                                err)) {
3924                                char *old_msg = strbuf_detach(err, NULL);
3925
3926                                strbuf_addf(err, "cannot update the ref '%s': %s",
3927                                            lock->ref_name, old_msg);
3928                                free(old_msg);
3929                                unlock_ref(lock);
3930                                update->backend_data = NULL;
3931                                ret = TRANSACTION_GENERIC_ERROR;
3932                                goto cleanup;
3933                        }
3934                }
3935                if (update->flags & REF_NEEDS_COMMIT) {
3936                        clear_loose_ref_cache(refs);
3937                        if (commit_ref(lock)) {
3938                                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
3939                                unlock_ref(lock);
3940                                update->backend_data = NULL;
3941                                ret = TRANSACTION_GENERIC_ERROR;
3942                                goto cleanup;
3943                        }
3944                }
3945        }
3946        /* Perform deletes now that updates are safely completed */
3947        for (i = 0; i < transaction->nr; i++) {
3948                struct ref_update *update = transaction->updates[i];
3949                struct ref_lock *lock = update->backend_data;
3950
3951                if (update->flags & REF_DELETING &&
3952                    !(update->flags & REF_LOG_ONLY)) {
3953                        if (!(update->type & REF_ISPACKED) ||
3954                            update->type & REF_ISSYMREF) {
3955                                /* It is a loose reference. */
3956                                strbuf_reset(&sb);
3957                                files_ref_path(refs, &sb, lock->ref_name);
3958                                if (unlink_or_msg(sb.buf, err)) {
3959                                        ret = TRANSACTION_GENERIC_ERROR;
3960                                        goto cleanup;
3961                                }
3962                                update->flags |= REF_DELETED_LOOSE;
3963                        }
3964
3965                        if (!(update->flags & REF_ISPRUNING))
3966                                string_list_append(&refs_to_delete,
3967                                                   lock->ref_name);
3968                }
3969        }
3970
3971        if (repack_without_refs(refs, &refs_to_delete, err)) {
3972                ret = TRANSACTION_GENERIC_ERROR;
3973                goto cleanup;
3974        }
3975
3976        /* Delete the reflogs of any references that were deleted: */
3977        for_each_string_list_item(ref_to_delete, &refs_to_delete) {
3978                strbuf_reset(&sb);
3979                files_reflog_path(refs, &sb, ref_to_delete->string);
3980                if (!unlink_or_warn(sb.buf))
3981                        try_remove_empty_parents(refs, ref_to_delete->string,
3982                                                 REMOVE_EMPTY_PARENTS_REFLOG);
3983        }
3984
3985        clear_loose_ref_cache(refs);
3986
3987cleanup:
3988        strbuf_release(&sb);
3989        transaction->state = REF_TRANSACTION_CLOSED;
3990
3991        for (i = 0; i < transaction->nr; i++) {
3992                struct ref_update *update = transaction->updates[i];
3993                struct ref_lock *lock = update->backend_data;
3994
3995                if (lock)
3996                        unlock_ref(lock);
3997
3998                if (update->flags & REF_DELETED_LOOSE) {
3999                        /*
4000                         * The loose reference was deleted. Delete any
4001                         * empty parent directories. (Note that this
4002                         * can only work because we have already
4003                         * removed the lockfile.)
4004                         */
4005                        try_remove_empty_parents(refs, update->refname,
4006                                                 REMOVE_EMPTY_PARENTS_REF);
4007                }
4008        }
4009
4010        string_list_clear(&refs_to_delete, 0);
4011        free(head_ref);
4012        string_list_clear(&affected_refnames, 0);
4013
4014        return ret;
4015}
4016
4017static int ref_present(const char *refname,
4018                       const struct object_id *oid, int flags, void *cb_data)
4019{
4020        struct string_list *affected_refnames = cb_data;
4021
4022        return string_list_has_string(affected_refnames, refname);
4023}
4024
4025static int files_initial_transaction_commit(struct ref_store *ref_store,
4026                                            struct ref_transaction *transaction,
4027                                            struct strbuf *err)
4028{
4029        struct files_ref_store *refs =
4030                files_downcast(ref_store, REF_STORE_WRITE,
4031                               "initial_ref_transaction_commit");
4032        int ret = 0, i;
4033        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
4034
4035        assert(err);
4036
4037        if (transaction->state != REF_TRANSACTION_OPEN)
4038                die("BUG: commit called for transaction that is not open");
4039
4040        /* Fail if a refname appears more than once in the transaction: */
4041        for (i = 0; i < transaction->nr; i++)
4042                string_list_append(&affected_refnames,
4043                                   transaction->updates[i]->refname);
4044        string_list_sort(&affected_refnames);
4045        if (ref_update_reject_duplicates(&affected_refnames, err)) {
4046                ret = TRANSACTION_GENERIC_ERROR;
4047                goto cleanup;
4048        }
4049
4050        /*
4051         * It's really undefined to call this function in an active
4052         * repository or when there are existing references: we are
4053         * only locking and changing packed-refs, so (1) any
4054         * simultaneous processes might try to change a reference at
4055         * the same time we do, and (2) any existing loose versions of
4056         * the references that we are setting would have precedence
4057         * over our values. But some remote helpers create the remote
4058         * "HEAD" and "master" branches before calling this function,
4059         * so here we really only check that none of the references
4060         * that we are creating already exists.
4061         */
4062        if (refs_for_each_rawref(&refs->base, ref_present,
4063                                 &affected_refnames))
4064                die("BUG: initial ref transaction called with existing refs");
4065
4066        for (i = 0; i < transaction->nr; i++) {
4067                struct ref_update *update = transaction->updates[i];
4068
4069                if ((update->flags & REF_HAVE_OLD) &&
4070                    !is_null_sha1(update->old_sha1))
4071                        die("BUG: initial ref transaction with old_sha1 set");
4072                if (refs_verify_refname_available(&refs->base, update->refname,
4073                                                  &affected_refnames, NULL,
4074                                                  err)) {
4075                        ret = TRANSACTION_NAME_CONFLICT;
4076                        goto cleanup;
4077                }
4078        }
4079
4080        if (lock_packed_refs(refs, 0)) {
4081                strbuf_addf(err, "unable to lock packed-refs file: %s",
4082                            strerror(errno));
4083                ret = TRANSACTION_GENERIC_ERROR;
4084                goto cleanup;
4085        }
4086
4087        for (i = 0; i < transaction->nr; i++) {
4088                struct ref_update *update = transaction->updates[i];
4089
4090                if ((update->flags & REF_HAVE_NEW) &&
4091                    !is_null_sha1(update->new_sha1))
4092                        add_packed_ref(refs, update->refname, update->new_sha1);
4093        }
4094
4095        if (commit_packed_refs(refs)) {
4096                strbuf_addf(err, "unable to commit packed-refs file: %s",
4097                            strerror(errno));
4098                ret = TRANSACTION_GENERIC_ERROR;
4099                goto cleanup;
4100        }
4101
4102cleanup:
4103        transaction->state = REF_TRANSACTION_CLOSED;
4104        string_list_clear(&affected_refnames, 0);
4105        return ret;
4106}
4107
4108struct expire_reflog_cb {
4109        unsigned int flags;
4110        reflog_expiry_should_prune_fn *should_prune_fn;
4111        void *policy_cb;
4112        FILE *newlog;
4113        struct object_id last_kept_oid;
4114};
4115
4116static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
4117                             const char *email, unsigned long timestamp, int tz,
4118                             const char *message, void *cb_data)
4119{
4120        struct expire_reflog_cb *cb = cb_data;
4121        struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
4122
4123        if (cb->flags & EXPIRE_REFLOGS_REWRITE)
4124                ooid = &cb->last_kept_oid;
4125
4126        if ((*cb->should_prune_fn)(ooid->hash, noid->hash, email, timestamp, tz,
4127                                   message, policy_cb)) {
4128                if (!cb->newlog)
4129                        printf("would prune %s", message);
4130                else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
4131                        printf("prune %s", message);
4132        } else {
4133                if (cb->newlog) {
4134                        fprintf(cb->newlog, "%s %s %s %lu %+05d\t%s",
4135                                oid_to_hex(ooid), oid_to_hex(noid),
4136                                email, timestamp, tz, message);
4137                        oidcpy(&cb->last_kept_oid, noid);
4138                }
4139                if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
4140                        printf("keep %s", message);
4141        }
4142        return 0;
4143}
4144
4145static int files_reflog_expire(struct ref_store *ref_store,
4146                               const char *refname, const unsigned char *sha1,
4147                               unsigned int flags,
4148                               reflog_expiry_prepare_fn prepare_fn,
4149                               reflog_expiry_should_prune_fn should_prune_fn,
4150                               reflog_expiry_cleanup_fn cleanup_fn,
4151                               void *policy_cb_data)
4152{
4153        struct files_ref_store *refs =
4154                files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
4155        static struct lock_file reflog_lock;
4156        struct expire_reflog_cb cb;
4157        struct ref_lock *lock;
4158        struct strbuf log_file_sb = STRBUF_INIT;
4159        char *log_file;
4160        int status = 0;
4161        int type;
4162        struct strbuf err = STRBUF_INIT;
4163
4164        memset(&cb, 0, sizeof(cb));
4165        cb.flags = flags;
4166        cb.policy_cb = policy_cb_data;
4167        cb.should_prune_fn = should_prune_fn;
4168
4169        /*
4170         * The reflog file is locked by holding the lock on the
4171         * reference itself, plus we might need to update the
4172         * reference if --updateref was specified:
4173         */
4174        lock = lock_ref_sha1_basic(refs, refname, sha1,
4175                                   NULL, NULL, REF_NODEREF,
4176                                   &type, &err);
4177        if (!lock) {
4178                error("cannot lock ref '%s': %s", refname, err.buf);
4179                strbuf_release(&err);
4180                return -1;
4181        }
4182        if (!refs_reflog_exists(ref_store, refname)) {
4183                unlock_ref(lock);
4184                return 0;
4185        }
4186
4187        files_reflog_path(refs, &log_file_sb, refname);
4188        log_file = strbuf_detach(&log_file_sb, NULL);
4189        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
4190                /*
4191                 * Even though holding $GIT_DIR/logs/$reflog.lock has
4192                 * no locking implications, we use the lock_file
4193                 * machinery here anyway because it does a lot of the
4194                 * work we need, including cleaning up if the program
4195                 * exits unexpectedly.
4196                 */
4197                if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
4198                        struct strbuf err = STRBUF_INIT;
4199                        unable_to_lock_message(log_file, errno, &err);
4200                        error("%s", err.buf);
4201                        strbuf_release(&err);
4202                        goto failure;
4203                }
4204                cb.newlog = fdopen_lock_file(&reflog_lock, "w");
4205                if (!cb.newlog) {
4206                        error("cannot fdopen %s (%s)",
4207                              get_lock_file_path(&reflog_lock), strerror(errno));
4208                        goto failure;
4209                }
4210        }
4211
4212        (*prepare_fn)(refname, sha1, cb.policy_cb);
4213        refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
4214        (*cleanup_fn)(cb.policy_cb);
4215
4216        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
4217                /*
4218                 * It doesn't make sense to adjust a reference pointed
4219                 * to by a symbolic ref based on expiring entries in
4220                 * the symbolic reference's reflog. Nor can we update
4221                 * a reference if there are no remaining reflog
4222                 * entries.
4223                 */
4224                int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
4225                        !(type & REF_ISSYMREF) &&
4226                        !is_null_oid(&cb.last_kept_oid);
4227
4228                if (close_lock_file(&reflog_lock)) {
4229                        status |= error("couldn't write %s: %s", log_file,
4230                                        strerror(errno));
4231                } else if (update &&
4232                           (write_in_full(get_lock_file_fd(lock->lk),
4233                                oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) != GIT_SHA1_HEXSZ ||
4234                            write_str_in_full(get_lock_file_fd(lock->lk), "\n") != 1 ||
4235                            close_ref(lock) < 0)) {
4236                        status |= error("couldn't write %s",
4237                                        get_lock_file_path(lock->lk));
4238                        rollback_lock_file(&reflog_lock);
4239                } else if (commit_lock_file(&reflog_lock)) {
4240                        status |= error("unable to write reflog '%s' (%s)",
4241                                        log_file, strerror(errno));
4242                } else if (update && commit_ref(lock)) {
4243                        status |= error("couldn't set %s", lock->ref_name);
4244                }
4245        }
4246        free(log_file);
4247        unlock_ref(lock);
4248        return status;
4249
4250 failure:
4251        rollback_lock_file(&reflog_lock);
4252        free(log_file);
4253        unlock_ref(lock);
4254        return -1;
4255}
4256
4257static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
4258{
4259        struct files_ref_store *refs =
4260                files_downcast(ref_store, REF_STORE_WRITE, "init_db");
4261        struct strbuf sb = STRBUF_INIT;
4262
4263        /*
4264         * Create .git/refs/{heads,tags}
4265         */
4266        files_ref_path(refs, &sb, "refs/heads");
4267        safe_create_dir(sb.buf, 1);
4268
4269        strbuf_reset(&sb);
4270        files_ref_path(refs, &sb, "refs/tags");
4271        safe_create_dir(sb.buf, 1);
4272
4273        strbuf_release(&sb);
4274        return 0;
4275}
4276
4277struct ref_storage_be refs_be_files = {
4278        NULL,
4279        "files",
4280        files_ref_store_create,
4281        files_init_db,
4282        files_transaction_commit,
4283        files_initial_transaction_commit,
4284
4285        files_pack_refs,
4286        files_peel_ref,
4287        files_create_symref,
4288        files_delete_refs,
4289        files_rename_ref,
4290
4291        files_ref_iterator_begin,
4292        files_read_raw_ref,
4293        files_verify_refname_available,
4294
4295        files_reflog_iterator_begin,
4296        files_for_each_reflog_ent,
4297        files_for_each_reflog_ent_reverse,
4298        files_reflog_exists,
4299        files_create_reflog,
4300        files_delete_reflog,
4301        files_reflog_expire
4302};