refs / files-backend.con commit Merge branch 'kn/ref-filter-branch-list' (0737780)
   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);
 168
 169static struct ref_dir *get_ref_dir(struct ref_entry *entry)
 170{
 171        struct ref_dir *dir;
 172        assert(entry->flag & REF_DIR);
 173        dir = &entry->u.subdir;
 174        if (entry->flag & REF_INCOMPLETE) {
 175                read_loose_refs(entry->name, dir);
 176
 177                /*
 178                 * Manually add refs/bisect, which, being
 179                 * per-worktree, might not appear in the directory
 180                 * listing for refs/ in the main repo.
 181                 */
 182                if (!strcmp(entry->name, "refs/")) {
 183                        int pos = search_ref_dir(dir, "refs/bisect/", 12);
 184                        if (pos < 0) {
 185                                struct ref_entry *child_entry;
 186                                child_entry = create_dir_entry(dir->ref_store,
 187                                                               "refs/bisect/",
 188                                                               12, 1);
 189                                add_entry_to_dir(dir, child_entry);
 190                                read_loose_refs("refs/bisect",
 191                                                &child_entry->u.subdir);
 192                        }
 193                }
 194                entry->flag &= ~REF_INCOMPLETE;
 195        }
 196        return dir;
 197}
 198
 199static struct ref_entry *create_ref_entry(const char *refname,
 200                                          const unsigned char *sha1, int flag,
 201                                          int check_name)
 202{
 203        struct ref_entry *ref;
 204
 205        if (check_name &&
 206            check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
 207                die("Reference has invalid format: '%s'", refname);
 208        FLEX_ALLOC_STR(ref, name, refname);
 209        hashcpy(ref->u.value.oid.hash, sha1);
 210        oidclr(&ref->u.value.peeled);
 211        ref->flag = flag;
 212        return ref;
 213}
 214
 215static void clear_ref_dir(struct ref_dir *dir);
 216
 217static void free_ref_entry(struct ref_entry *entry)
 218{
 219        if (entry->flag & REF_DIR) {
 220                /*
 221                 * Do not use get_ref_dir() here, as that might
 222                 * trigger the reading of loose refs.
 223                 */
 224                clear_ref_dir(&entry->u.subdir);
 225        }
 226        free(entry);
 227}
 228
 229/*
 230 * Add a ref_entry to the end of dir (unsorted).  Entry is always
 231 * stored directly in dir; no recursion into subdirectories is
 232 * done.
 233 */
 234static void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry)
 235{
 236        ALLOC_GROW(dir->entries, dir->nr + 1, dir->alloc);
 237        dir->entries[dir->nr++] = entry;
 238        /* optimize for the case that entries are added in order */
 239        if (dir->nr == 1 ||
 240            (dir->nr == dir->sorted + 1 &&
 241             strcmp(dir->entries[dir->nr - 2]->name,
 242                    dir->entries[dir->nr - 1]->name) < 0))
 243                dir->sorted = dir->nr;
 244}
 245
 246/*
 247 * Clear and free all entries in dir, recursively.
 248 */
 249static void clear_ref_dir(struct ref_dir *dir)
 250{
 251        int i;
 252        for (i = 0; i < dir->nr; i++)
 253                free_ref_entry(dir->entries[i]);
 254        free(dir->entries);
 255        dir->sorted = dir->nr = dir->alloc = 0;
 256        dir->entries = NULL;
 257}
 258
 259/*
 260 * Create a struct ref_entry object for the specified dirname.
 261 * dirname is the name of the directory with a trailing slash (e.g.,
 262 * "refs/heads/") or "" for the top-level directory.
 263 */
 264static struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
 265                                          const char *dirname, size_t len,
 266                                          int incomplete)
 267{
 268        struct ref_entry *direntry;
 269        FLEX_ALLOC_MEM(direntry, name, dirname, len);
 270        direntry->u.subdir.ref_store = ref_store;
 271        direntry->flag = REF_DIR | (incomplete ? REF_INCOMPLETE : 0);
 272        return direntry;
 273}
 274
 275static int ref_entry_cmp(const void *a, const void *b)
 276{
 277        struct ref_entry *one = *(struct ref_entry **)a;
 278        struct ref_entry *two = *(struct ref_entry **)b;
 279        return strcmp(one->name, two->name);
 280}
 281
 282static void sort_ref_dir(struct ref_dir *dir);
 283
 284struct string_slice {
 285        size_t len;
 286        const char *str;
 287};
 288
 289static int ref_entry_cmp_sslice(const void *key_, const void *ent_)
 290{
 291        const struct string_slice *key = key_;
 292        const struct ref_entry *ent = *(const struct ref_entry * const *)ent_;
 293        int cmp = strncmp(key->str, ent->name, key->len);
 294        if (cmp)
 295                return cmp;
 296        return '\0' - (unsigned char)ent->name[key->len];
 297}
 298
 299/*
 300 * Return the index of the entry with the given refname from the
 301 * ref_dir (non-recursively), sorting dir if necessary.  Return -1 if
 302 * no such entry is found.  dir must already be complete.
 303 */
 304static int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len)
 305{
 306        struct ref_entry **r;
 307        struct string_slice key;
 308
 309        if (refname == NULL || !dir->nr)
 310                return -1;
 311
 312        sort_ref_dir(dir);
 313        key.len = len;
 314        key.str = refname;
 315        r = bsearch(&key, dir->entries, dir->nr, sizeof(*dir->entries),
 316                    ref_entry_cmp_sslice);
 317
 318        if (r == NULL)
 319                return -1;
 320
 321        return r - dir->entries;
 322}
 323
 324/*
 325 * Search for a directory entry directly within dir (without
 326 * recursing).  Sort dir if necessary.  subdirname must be a directory
 327 * name (i.e., end in '/').  If mkdir is set, then create the
 328 * directory if it is missing; otherwise, return NULL if the desired
 329 * directory cannot be found.  dir must already be complete.
 330 */
 331static struct ref_dir *search_for_subdir(struct ref_dir *dir,
 332                                         const char *subdirname, size_t len,
 333                                         int mkdir)
 334{
 335        int entry_index = search_ref_dir(dir, subdirname, len);
 336        struct ref_entry *entry;
 337        if (entry_index == -1) {
 338                if (!mkdir)
 339                        return NULL;
 340                /*
 341                 * Since dir is complete, the absence of a subdir
 342                 * means that the subdir really doesn't exist;
 343                 * therefore, create an empty record for it but mark
 344                 * the record complete.
 345                 */
 346                entry = create_dir_entry(dir->ref_store, subdirname, len, 0);
 347                add_entry_to_dir(dir, entry);
 348        } else {
 349                entry = dir->entries[entry_index];
 350        }
 351        return get_ref_dir(entry);
 352}
 353
 354/*
 355 * If refname is a reference name, find the ref_dir within the dir
 356 * tree that should hold refname.  If refname is a directory name
 357 * (i.e., ends in '/'), then return that ref_dir itself.  dir must
 358 * represent the top-level directory and must already be complete.
 359 * Sort ref_dirs and recurse into subdirectories as necessary.  If
 360 * mkdir is set, then create any missing directories; otherwise,
 361 * return NULL if the desired directory cannot be found.
 362 */
 363static struct ref_dir *find_containing_dir(struct ref_dir *dir,
 364                                           const char *refname, int mkdir)
 365{
 366        const char *slash;
 367        for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) {
 368                size_t dirnamelen = slash - refname + 1;
 369                struct ref_dir *subdir;
 370                subdir = search_for_subdir(dir, refname, dirnamelen, mkdir);
 371                if (!subdir) {
 372                        dir = NULL;
 373                        break;
 374                }
 375                dir = subdir;
 376        }
 377
 378        return dir;
 379}
 380
 381/*
 382 * Find the value entry with the given name in dir, sorting ref_dirs
 383 * and recursing into subdirectories as necessary.  If the name is not
 384 * found or it corresponds to a directory entry, return NULL.
 385 */
 386static struct ref_entry *find_ref(struct ref_dir *dir, const char *refname)
 387{
 388        int entry_index;
 389        struct ref_entry *entry;
 390        dir = find_containing_dir(dir, refname, 0);
 391        if (!dir)
 392                return NULL;
 393        entry_index = search_ref_dir(dir, refname, strlen(refname));
 394        if (entry_index == -1)
 395                return NULL;
 396        entry = dir->entries[entry_index];
 397        return (entry->flag & REF_DIR) ? NULL : entry;
 398}
 399
 400/*
 401 * Remove the entry with the given name from dir, recursing into
 402 * subdirectories as necessary.  If refname is the name of a directory
 403 * (i.e., ends with '/'), then remove the directory and its contents.
 404 * If the removal was successful, return the number of entries
 405 * remaining in the directory entry that contained the deleted entry.
 406 * If the name was not found, return -1.  Please note that this
 407 * function only deletes the entry from the cache; it does not delete
 408 * it from the filesystem or ensure that other cache entries (which
 409 * might be symbolic references to the removed entry) are updated.
 410 * Nor does it remove any containing dir entries that might be made
 411 * empty by the removal.  dir must represent the top-level directory
 412 * and must already be complete.
 413 */
 414static int remove_entry(struct ref_dir *dir, const char *refname)
 415{
 416        int refname_len = strlen(refname);
 417        int entry_index;
 418        struct ref_entry *entry;
 419        int is_dir = refname[refname_len - 1] == '/';
 420        if (is_dir) {
 421                /*
 422                 * refname represents a reference directory.  Remove
 423                 * the trailing slash; otherwise we will get the
 424                 * directory *representing* refname rather than the
 425                 * one *containing* it.
 426                 */
 427                char *dirname = xmemdupz(refname, refname_len - 1);
 428                dir = find_containing_dir(dir, dirname, 0);
 429                free(dirname);
 430        } else {
 431                dir = find_containing_dir(dir, refname, 0);
 432        }
 433        if (!dir)
 434                return -1;
 435        entry_index = search_ref_dir(dir, refname, refname_len);
 436        if (entry_index == -1)
 437                return -1;
 438        entry = dir->entries[entry_index];
 439
 440        memmove(&dir->entries[entry_index],
 441                &dir->entries[entry_index + 1],
 442                (dir->nr - entry_index - 1) * sizeof(*dir->entries)
 443                );
 444        dir->nr--;
 445        if (dir->sorted > entry_index)
 446                dir->sorted--;
 447        free_ref_entry(entry);
 448        return dir->nr;
 449}
 450
 451/*
 452 * Add a ref_entry to the ref_dir (unsorted), recursing into
 453 * subdirectories as necessary.  dir must represent the top-level
 454 * directory.  Return 0 on success.
 455 */
 456static int add_ref(struct ref_dir *dir, struct ref_entry *ref)
 457{
 458        dir = find_containing_dir(dir, ref->name, 1);
 459        if (!dir)
 460                return -1;
 461        add_entry_to_dir(dir, ref);
 462        return 0;
 463}
 464
 465/*
 466 * Emit a warning and return true iff ref1 and ref2 have the same name
 467 * and the same sha1.  Die if they have the same name but different
 468 * sha1s.
 469 */
 470static int is_dup_ref(const struct ref_entry *ref1, const struct ref_entry *ref2)
 471{
 472        if (strcmp(ref1->name, ref2->name))
 473                return 0;
 474
 475        /* Duplicate name; make sure that they don't conflict: */
 476
 477        if ((ref1->flag & REF_DIR) || (ref2->flag & REF_DIR))
 478                /* This is impossible by construction */
 479                die("Reference directory conflict: %s", ref1->name);
 480
 481        if (oidcmp(&ref1->u.value.oid, &ref2->u.value.oid))
 482                die("Duplicated ref, and SHA1s don't match: %s", ref1->name);
 483
 484        warning("Duplicated ref: %s", ref1->name);
 485        return 1;
 486}
 487
 488/*
 489 * Sort the entries in dir non-recursively (if they are not already
 490 * sorted) and remove any duplicate entries.
 491 */
 492static void sort_ref_dir(struct ref_dir *dir)
 493{
 494        int i, j;
 495        struct ref_entry *last = NULL;
 496
 497        /*
 498         * This check also prevents passing a zero-length array to qsort(),
 499         * which is a problem on some platforms.
 500         */
 501        if (dir->sorted == dir->nr)
 502                return;
 503
 504        QSORT(dir->entries, dir->nr, ref_entry_cmp);
 505
 506        /* Remove any duplicates: */
 507        for (i = 0, j = 0; j < dir->nr; j++) {
 508                struct ref_entry *entry = dir->entries[j];
 509                if (last && is_dup_ref(last, entry))
 510                        free_ref_entry(entry);
 511                else
 512                        last = dir->entries[i++] = entry;
 513        }
 514        dir->sorted = dir->nr = i;
 515}
 516
 517/*
 518 * Return true if refname, which has the specified oid and flags, can
 519 * be resolved to an object in the database. If the referred-to object
 520 * does not exist, emit a warning and return false.
 521 */
 522static int ref_resolves_to_object(const char *refname,
 523                                  const struct object_id *oid,
 524                                  unsigned int flags)
 525{
 526        if (flags & REF_ISBROKEN)
 527                return 0;
 528        if (!has_sha1_file(oid->hash)) {
 529                error("%s does not point to a valid object!", refname);
 530                return 0;
 531        }
 532        return 1;
 533}
 534
 535/*
 536 * Return true if the reference described by entry can be resolved to
 537 * an object in the database; otherwise, emit a warning and return
 538 * false.
 539 */
 540static int entry_resolves_to_object(struct ref_entry *entry)
 541{
 542        return ref_resolves_to_object(entry->name,
 543                                      &entry->u.value.oid, entry->flag);
 544}
 545
 546typedef int each_ref_entry_fn(struct ref_entry *entry, void *cb_data);
 547
 548/*
 549 * Call fn for each reference in dir that has index in the range
 550 * offset <= index < dir->nr.  Recurse into subdirectories that are in
 551 * that index range, sorting them before iterating.  This function
 552 * does not sort dir itself; it should be sorted beforehand.  fn is
 553 * called for all references, including broken ones.
 554 */
 555static int do_for_each_entry_in_dir(struct ref_dir *dir, int offset,
 556                                    each_ref_entry_fn fn, void *cb_data)
 557{
 558        int i;
 559        assert(dir->sorted == dir->nr);
 560        for (i = offset; i < dir->nr; i++) {
 561                struct ref_entry *entry = dir->entries[i];
 562                int retval;
 563                if (entry->flag & REF_DIR) {
 564                        struct ref_dir *subdir = get_ref_dir(entry);
 565                        sort_ref_dir(subdir);
 566                        retval = do_for_each_entry_in_dir(subdir, 0, fn, cb_data);
 567                } else {
 568                        retval = fn(entry, cb_data);
 569                }
 570                if (retval)
 571                        return retval;
 572        }
 573        return 0;
 574}
 575
 576/*
 577 * Load all of the refs from the dir into our in-memory cache. The hard work
 578 * of loading loose refs is done by get_ref_dir(), so we just need to recurse
 579 * through all of the sub-directories. We do not even need to care about
 580 * sorting, as traversal order does not matter to us.
 581 */
 582static void prime_ref_dir(struct ref_dir *dir)
 583{
 584        int i;
 585        for (i = 0; i < dir->nr; i++) {
 586                struct ref_entry *entry = dir->entries[i];
 587                if (entry->flag & REF_DIR)
 588                        prime_ref_dir(get_ref_dir(entry));
 589        }
 590}
 591
 592/*
 593 * A level in the reference hierarchy that is currently being iterated
 594 * through.
 595 */
 596struct cache_ref_iterator_level {
 597        /*
 598         * The ref_dir being iterated over at this level. The ref_dir
 599         * is sorted before being stored here.
 600         */
 601        struct ref_dir *dir;
 602
 603        /*
 604         * The index of the current entry within dir (which might
 605         * itself be a directory). If index == -1, then the iteration
 606         * hasn't yet begun. If index == dir->nr, then the iteration
 607         * through this level is over.
 608         */
 609        int index;
 610};
 611
 612/*
 613 * Represent an iteration through a ref_dir in the memory cache. The
 614 * iteration recurses through subdirectories.
 615 */
 616struct cache_ref_iterator {
 617        struct ref_iterator base;
 618
 619        /*
 620         * The number of levels currently on the stack. This is always
 621         * at least 1, because when it becomes zero the iteration is
 622         * ended and this struct is freed.
 623         */
 624        size_t levels_nr;
 625
 626        /* The number of levels that have been allocated on the stack */
 627        size_t levels_alloc;
 628
 629        /*
 630         * A stack of levels. levels[0] is the uppermost level that is
 631         * being iterated over in this iteration. (This is not
 632         * necessary the top level in the references hierarchy. If we
 633         * are iterating through a subtree, then levels[0] will hold
 634         * the ref_dir for that subtree, and subsequent levels will go
 635         * on from there.)
 636         */
 637        struct cache_ref_iterator_level *levels;
 638};
 639
 640static int cache_ref_iterator_advance(struct ref_iterator *ref_iterator)
 641{
 642        struct cache_ref_iterator *iter =
 643                (struct cache_ref_iterator *)ref_iterator;
 644
 645        while (1) {
 646                struct cache_ref_iterator_level *level =
 647                        &iter->levels[iter->levels_nr - 1];
 648                struct ref_dir *dir = level->dir;
 649                struct ref_entry *entry;
 650
 651                if (level->index == -1)
 652                        sort_ref_dir(dir);
 653
 654                if (++level->index == level->dir->nr) {
 655                        /* This level is exhausted; pop up a level */
 656                        if (--iter->levels_nr == 0)
 657                                return ref_iterator_abort(ref_iterator);
 658
 659                        continue;
 660                }
 661
 662                entry = dir->entries[level->index];
 663
 664                if (entry->flag & REF_DIR) {
 665                        /* push down a level */
 666                        ALLOC_GROW(iter->levels, iter->levels_nr + 1,
 667                                   iter->levels_alloc);
 668
 669                        level = &iter->levels[iter->levels_nr++];
 670                        level->dir = get_ref_dir(entry);
 671                        level->index = -1;
 672                } else {
 673                        iter->base.refname = entry->name;
 674                        iter->base.oid = &entry->u.value.oid;
 675                        iter->base.flags = entry->flag;
 676                        return ITER_OK;
 677                }
 678        }
 679}
 680
 681static enum peel_status peel_entry(struct ref_entry *entry, int repeel);
 682
 683static int cache_ref_iterator_peel(struct ref_iterator *ref_iterator,
 684                                   struct object_id *peeled)
 685{
 686        struct cache_ref_iterator *iter =
 687                (struct cache_ref_iterator *)ref_iterator;
 688        struct cache_ref_iterator_level *level;
 689        struct ref_entry *entry;
 690
 691        level = &iter->levels[iter->levels_nr - 1];
 692
 693        if (level->index == -1)
 694                die("BUG: peel called before advance for cache iterator");
 695
 696        entry = level->dir->entries[level->index];
 697
 698        if (peel_entry(entry, 0))
 699                return -1;
 700        oidcpy(peeled, &entry->u.value.peeled);
 701        return 0;
 702}
 703
 704static int cache_ref_iterator_abort(struct ref_iterator *ref_iterator)
 705{
 706        struct cache_ref_iterator *iter =
 707                (struct cache_ref_iterator *)ref_iterator;
 708
 709        free(iter->levels);
 710        base_ref_iterator_free(ref_iterator);
 711        return ITER_DONE;
 712}
 713
 714static struct ref_iterator_vtable cache_ref_iterator_vtable = {
 715        cache_ref_iterator_advance,
 716        cache_ref_iterator_peel,
 717        cache_ref_iterator_abort
 718};
 719
 720static struct ref_iterator *cache_ref_iterator_begin(struct ref_dir *dir)
 721{
 722        struct cache_ref_iterator *iter;
 723        struct ref_iterator *ref_iterator;
 724        struct cache_ref_iterator_level *level;
 725
 726        iter = xcalloc(1, sizeof(*iter));
 727        ref_iterator = &iter->base;
 728        base_ref_iterator_init(ref_iterator, &cache_ref_iterator_vtable);
 729        ALLOC_GROW(iter->levels, 10, iter->levels_alloc);
 730
 731        iter->levels_nr = 1;
 732        level = &iter->levels[0];
 733        level->index = -1;
 734        level->dir = dir;
 735
 736        return ref_iterator;
 737}
 738
 739struct nonmatching_ref_data {
 740        const struct string_list *skip;
 741        const char *conflicting_refname;
 742};
 743
 744static int nonmatching_ref_fn(struct ref_entry *entry, void *vdata)
 745{
 746        struct nonmatching_ref_data *data = vdata;
 747
 748        if (data->skip && string_list_has_string(data->skip, entry->name))
 749                return 0;
 750
 751        data->conflicting_refname = entry->name;
 752        return 1;
 753}
 754
 755/*
 756 * Return 0 if a reference named refname could be created without
 757 * conflicting with the name of an existing reference in dir.
 758 * See verify_refname_available for more information.
 759 */
 760static int verify_refname_available_dir(const char *refname,
 761                                        const struct string_list *extras,
 762                                        const struct string_list *skip,
 763                                        struct ref_dir *dir,
 764                                        struct strbuf *err)
 765{
 766        const char *slash;
 767        const char *extra_refname;
 768        int pos;
 769        struct strbuf dirname = STRBUF_INIT;
 770        int ret = -1;
 771
 772        /*
 773         * For the sake of comments in this function, suppose that
 774         * refname is "refs/foo/bar".
 775         */
 776
 777        assert(err);
 778
 779        strbuf_grow(&dirname, strlen(refname) + 1);
 780        for (slash = strchr(refname, '/'); slash; slash = strchr(slash + 1, '/')) {
 781                /* Expand dirname to the new prefix, not including the trailing slash: */
 782                strbuf_add(&dirname, refname + dirname.len, slash - refname - dirname.len);
 783
 784                /*
 785                 * We are still at a leading dir of the refname (e.g.,
 786                 * "refs/foo"; if there is a reference with that name,
 787                 * it is a conflict, *unless* it is in skip.
 788                 */
 789                if (dir) {
 790                        pos = search_ref_dir(dir, dirname.buf, dirname.len);
 791                        if (pos >= 0 &&
 792                            (!skip || !string_list_has_string(skip, dirname.buf))) {
 793                                /*
 794                                 * We found a reference whose name is
 795                                 * a proper prefix of refname; e.g.,
 796                                 * "refs/foo", and is not in skip.
 797                                 */
 798                                strbuf_addf(err, "'%s' exists; cannot create '%s'",
 799                                            dirname.buf, refname);
 800                                goto cleanup;
 801                        }
 802                }
 803
 804                if (extras && string_list_has_string(extras, dirname.buf) &&
 805                    (!skip || !string_list_has_string(skip, dirname.buf))) {
 806                        strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
 807                                    refname, dirname.buf);
 808                        goto cleanup;
 809                }
 810
 811                /*
 812                 * Otherwise, we can try to continue our search with
 813                 * the next component. So try to look up the
 814                 * directory, e.g., "refs/foo/". If we come up empty,
 815                 * we know there is nothing under this whole prefix,
 816                 * but even in that case we still have to continue the
 817                 * search for conflicts with extras.
 818                 */
 819                strbuf_addch(&dirname, '/');
 820                if (dir) {
 821                        pos = search_ref_dir(dir, dirname.buf, dirname.len);
 822                        if (pos < 0) {
 823                                /*
 824                                 * There was no directory "refs/foo/",
 825                                 * so there is nothing under this
 826                                 * whole prefix. So there is no need
 827                                 * to continue looking for conflicting
 828                                 * references. But we need to continue
 829                                 * looking for conflicting extras.
 830                                 */
 831                                dir = NULL;
 832                        } else {
 833                                dir = get_ref_dir(dir->entries[pos]);
 834                        }
 835                }
 836        }
 837
 838        /*
 839         * We are at the leaf of our refname (e.g., "refs/foo/bar").
 840         * There is no point in searching for a reference with that
 841         * name, because a refname isn't considered to conflict with
 842         * itself. But we still need to check for references whose
 843         * names are in the "refs/foo/bar/" namespace, because they
 844         * *do* conflict.
 845         */
 846        strbuf_addstr(&dirname, refname + dirname.len);
 847        strbuf_addch(&dirname, '/');
 848
 849        if (dir) {
 850                pos = search_ref_dir(dir, dirname.buf, dirname.len);
 851
 852                if (pos >= 0) {
 853                        /*
 854                         * We found a directory named "$refname/"
 855                         * (e.g., "refs/foo/bar/"). It is a problem
 856                         * iff it contains any ref that is not in
 857                         * "skip".
 858                         */
 859                        struct nonmatching_ref_data data;
 860
 861                        data.skip = skip;
 862                        data.conflicting_refname = NULL;
 863                        dir = get_ref_dir(dir->entries[pos]);
 864                        sort_ref_dir(dir);
 865                        if (do_for_each_entry_in_dir(dir, 0, nonmatching_ref_fn, &data)) {
 866                                strbuf_addf(err, "'%s' exists; cannot create '%s'",
 867                                            data.conflicting_refname, refname);
 868                                goto cleanup;
 869                        }
 870                }
 871        }
 872
 873        extra_refname = find_descendant_ref(dirname.buf, extras, skip);
 874        if (extra_refname)
 875                strbuf_addf(err, "cannot process '%s' and '%s' at the same time",
 876                            refname, extra_refname);
 877        else
 878                ret = 0;
 879
 880cleanup:
 881        strbuf_release(&dirname);
 882        return ret;
 883}
 884
 885struct packed_ref_cache {
 886        struct ref_entry *root;
 887
 888        /*
 889         * Count of references to the data structure in this instance,
 890         * including the pointer from files_ref_store::packed if any.
 891         * The data will not be freed as long as the reference count
 892         * is nonzero.
 893         */
 894        unsigned int referrers;
 895
 896        /*
 897         * Iff the packed-refs file associated with this instance is
 898         * currently locked for writing, this points at the associated
 899         * lock (which is owned by somebody else).  The referrer count
 900         * is also incremented when the file is locked and decremented
 901         * when it is unlocked.
 902         */
 903        struct lock_file *lock;
 904
 905        /* The metadata from when this packed-refs cache was read */
 906        struct stat_validity validity;
 907};
 908
 909/*
 910 * Future: need to be in "struct repository"
 911 * when doing a full libification.
 912 */
 913struct files_ref_store {
 914        struct ref_store base;
 915
 916        /*
 917         * The name of the submodule represented by this object, or
 918         * NULL if it represents the main repository's reference
 919         * store:
 920         */
 921        const char *submodule;
 922
 923        struct ref_entry *loose;
 924        struct packed_ref_cache *packed;
 925};
 926
 927/* Lock used for the main packed-refs file: */
 928static struct lock_file packlock;
 929
 930/*
 931 * Increment the reference count of *packed_refs.
 932 */
 933static void acquire_packed_ref_cache(struct packed_ref_cache *packed_refs)
 934{
 935        packed_refs->referrers++;
 936}
 937
 938/*
 939 * Decrease the reference count of *packed_refs.  If it goes to zero,
 940 * free *packed_refs and return true; otherwise return false.
 941 */
 942static int release_packed_ref_cache(struct packed_ref_cache *packed_refs)
 943{
 944        if (!--packed_refs->referrers) {
 945                free_ref_entry(packed_refs->root);
 946                stat_validity_clear(&packed_refs->validity);
 947                free(packed_refs);
 948                return 1;
 949        } else {
 950                return 0;
 951        }
 952}
 953
 954static void clear_packed_ref_cache(struct files_ref_store *refs)
 955{
 956        if (refs->packed) {
 957                struct packed_ref_cache *packed_refs = refs->packed;
 958
 959                if (packed_refs->lock)
 960                        die("internal error: packed-ref cache cleared while locked");
 961                refs->packed = NULL;
 962                release_packed_ref_cache(packed_refs);
 963        }
 964}
 965
 966static void clear_loose_ref_cache(struct files_ref_store *refs)
 967{
 968        if (refs->loose) {
 969                free_ref_entry(refs->loose);
 970                refs->loose = NULL;
 971        }
 972}
 973
 974/*
 975 * Create a new submodule ref cache and add it to the internal
 976 * set of caches.
 977 */
 978static struct ref_store *files_ref_store_create(const char *submodule)
 979{
 980        struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
 981        struct ref_store *ref_store = (struct ref_store *)refs;
 982
 983        base_ref_store_init(ref_store, &refs_be_files);
 984
 985        refs->submodule = xstrdup_or_null(submodule);
 986
 987        return ref_store;
 988}
 989
 990/*
 991 * Die if refs is for a submodule (i.e., not for the main repository).
 992 * caller is used in any necessary error messages.
 993 */
 994static void files_assert_main_repository(struct files_ref_store *refs,
 995                                         const char *caller)
 996{
 997        if (refs->submodule)
 998                die("BUG: %s called for a submodule", caller);
 999}
1000
1001/*
1002 * Downcast ref_store to files_ref_store. Die if ref_store is not a
1003 * files_ref_store. If submodule_allowed is not true, then also die if
1004 * files_ref_store is for a submodule (i.e., not for the main
1005 * repository). caller is used in any necessary error messages.
1006 */
1007static struct files_ref_store *files_downcast(
1008                struct ref_store *ref_store, int submodule_allowed,
1009                const char *caller)
1010{
1011        struct files_ref_store *refs;
1012
1013        if (ref_store->be != &refs_be_files)
1014                die("BUG: ref_store is type \"%s\" not \"files\" in %s",
1015                    ref_store->be->name, caller);
1016
1017        refs = (struct files_ref_store *)ref_store;
1018
1019        if (!submodule_allowed)
1020                files_assert_main_repository(refs, caller);
1021
1022        return refs;
1023}
1024
1025/* The length of a peeled reference line in packed-refs, including EOL: */
1026#define PEELED_LINE_LENGTH 42
1027
1028/*
1029 * The packed-refs header line that we write out.  Perhaps other
1030 * traits will be added later.  The trailing space is required.
1031 */
1032static const char PACKED_REFS_HEADER[] =
1033        "# pack-refs with: peeled fully-peeled \n";
1034
1035/*
1036 * Parse one line from a packed-refs file.  Write the SHA1 to sha1.
1037 * Return a pointer to the refname within the line (null-terminated),
1038 * or NULL if there was a problem.
1039 */
1040static const char *parse_ref_line(struct strbuf *line, unsigned char *sha1)
1041{
1042        const char *ref;
1043
1044        /*
1045         * 42: the answer to everything.
1046         *
1047         * In this case, it happens to be the answer to
1048         *  40 (length of sha1 hex representation)
1049         *  +1 (space in between hex and name)
1050         *  +1 (newline at the end of the line)
1051         */
1052        if (line->len <= 42)
1053                return NULL;
1054
1055        if (get_sha1_hex(line->buf, sha1) < 0)
1056                return NULL;
1057        if (!isspace(line->buf[40]))
1058                return NULL;
1059
1060        ref = line->buf + 41;
1061        if (isspace(*ref))
1062                return NULL;
1063
1064        if (line->buf[line->len - 1] != '\n')
1065                return NULL;
1066        line->buf[--line->len] = 0;
1067
1068        return ref;
1069}
1070
1071/*
1072 * Read f, which is a packed-refs file, into dir.
1073 *
1074 * A comment line of the form "# pack-refs with: " may contain zero or
1075 * more traits. We interpret the traits as follows:
1076 *
1077 *   No traits:
1078 *
1079 *      Probably no references are peeled. But if the file contains a
1080 *      peeled value for a reference, we will use it.
1081 *
1082 *   peeled:
1083 *
1084 *      References under "refs/tags/", if they *can* be peeled, *are*
1085 *      peeled in this file. References outside of "refs/tags/" are
1086 *      probably not peeled even if they could have been, but if we find
1087 *      a peeled value for such a reference we will use it.
1088 *
1089 *   fully-peeled:
1090 *
1091 *      All references in the file that can be peeled are peeled.
1092 *      Inversely (and this is more important), any references in the
1093 *      file for which no peeled value is recorded is not peelable. This
1094 *      trait should typically be written alongside "peeled" for
1095 *      compatibility with older clients, but we do not require it
1096 *      (i.e., "peeled" is a no-op if "fully-peeled" is set).
1097 */
1098static void read_packed_refs(FILE *f, struct ref_dir *dir)
1099{
1100        struct ref_entry *last = NULL;
1101        struct strbuf line = STRBUF_INIT;
1102        enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled = PEELED_NONE;
1103
1104        while (strbuf_getwholeline(&line, f, '\n') != EOF) {
1105                unsigned char sha1[20];
1106                const char *refname;
1107                const char *traits;
1108
1109                if (skip_prefix(line.buf, "# pack-refs with:", &traits)) {
1110                        if (strstr(traits, " fully-peeled "))
1111                                peeled = PEELED_FULLY;
1112                        else if (strstr(traits, " peeled "))
1113                                peeled = PEELED_TAGS;
1114                        /* perhaps other traits later as well */
1115                        continue;
1116                }
1117
1118                refname = parse_ref_line(&line, sha1);
1119                if (refname) {
1120                        int flag = REF_ISPACKED;
1121
1122                        if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
1123                                if (!refname_is_safe(refname))
1124                                        die("packed refname is dangerous: %s", refname);
1125                                hashclr(sha1);
1126                                flag |= REF_BAD_NAME | REF_ISBROKEN;
1127                        }
1128                        last = create_ref_entry(refname, sha1, flag, 0);
1129                        if (peeled == PEELED_FULLY ||
1130                            (peeled == PEELED_TAGS && starts_with(refname, "refs/tags/")))
1131                                last->flag |= REF_KNOWS_PEELED;
1132                        add_ref(dir, last);
1133                        continue;
1134                }
1135                if (last &&
1136                    line.buf[0] == '^' &&
1137                    line.len == PEELED_LINE_LENGTH &&
1138                    line.buf[PEELED_LINE_LENGTH - 1] == '\n' &&
1139                    !get_sha1_hex(line.buf + 1, sha1)) {
1140                        hashcpy(last->u.value.peeled.hash, sha1);
1141                        /*
1142                         * Regardless of what the file header said,
1143                         * we definitely know the value of *this*
1144                         * reference:
1145                         */
1146                        last->flag |= REF_KNOWS_PEELED;
1147                }
1148        }
1149
1150        strbuf_release(&line);
1151}
1152
1153/*
1154 * Get the packed_ref_cache for the specified files_ref_store,
1155 * creating it if necessary.
1156 */
1157static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *refs)
1158{
1159        char *packed_refs_file;
1160
1161        if (refs->submodule)
1162                packed_refs_file = git_pathdup_submodule(refs->submodule,
1163                                                         "packed-refs");
1164        else
1165                packed_refs_file = git_pathdup("packed-refs");
1166
1167        if (refs->packed &&
1168            !stat_validity_check(&refs->packed->validity, packed_refs_file))
1169                clear_packed_ref_cache(refs);
1170
1171        if (!refs->packed) {
1172                FILE *f;
1173
1174                refs->packed = xcalloc(1, sizeof(*refs->packed));
1175                acquire_packed_ref_cache(refs->packed);
1176                refs->packed->root = create_dir_entry(refs, "", 0, 0);
1177                f = fopen(packed_refs_file, "r");
1178                if (f) {
1179                        stat_validity_update(&refs->packed->validity, fileno(f));
1180                        read_packed_refs(f, get_ref_dir(refs->packed->root));
1181                        fclose(f);
1182                }
1183        }
1184        free(packed_refs_file);
1185        return refs->packed;
1186}
1187
1188static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_cache)
1189{
1190        return get_ref_dir(packed_ref_cache->root);
1191}
1192
1193static struct ref_dir *get_packed_refs(struct files_ref_store *refs)
1194{
1195        return get_packed_ref_dir(get_packed_ref_cache(refs));
1196}
1197
1198/*
1199 * Add a reference to the in-memory packed reference cache.  This may
1200 * only be called while the packed-refs file is locked (see
1201 * lock_packed_refs()).  To actually write the packed-refs file, call
1202 * commit_packed_refs().
1203 */
1204static void add_packed_ref(struct files_ref_store *refs,
1205                           const char *refname, const unsigned char *sha1)
1206{
1207        struct packed_ref_cache *packed_ref_cache = get_packed_ref_cache(refs);
1208
1209        if (!packed_ref_cache->lock)
1210                die("internal error: packed refs not locked");
1211        add_ref(get_packed_ref_dir(packed_ref_cache),
1212                create_ref_entry(refname, sha1, REF_ISPACKED, 1));
1213}
1214
1215/*
1216 * Read the loose references from the namespace dirname into dir
1217 * (without recursing).  dirname must end with '/'.  dir must be the
1218 * directory entry corresponding to dirname.
1219 */
1220static void read_loose_refs(const char *dirname, struct ref_dir *dir)
1221{
1222        struct files_ref_store *refs = dir->ref_store;
1223        DIR *d;
1224        struct dirent *de;
1225        int dirnamelen = strlen(dirname);
1226        struct strbuf refname;
1227        struct strbuf path = STRBUF_INIT;
1228        size_t path_baselen;
1229        int err = 0;
1230
1231        if (refs->submodule)
1232                err = strbuf_git_path_submodule(&path, refs->submodule, "%s", dirname);
1233        else
1234                strbuf_git_path(&path, "%s", dirname);
1235        path_baselen = path.len;
1236
1237        if (err) {
1238                strbuf_release(&path);
1239                return;
1240        }
1241
1242        d = opendir(path.buf);
1243        if (!d) {
1244                strbuf_release(&path);
1245                return;
1246        }
1247
1248        strbuf_init(&refname, dirnamelen + 257);
1249        strbuf_add(&refname, dirname, dirnamelen);
1250
1251        while ((de = readdir(d)) != NULL) {
1252                unsigned char sha1[20];
1253                struct stat st;
1254                int flag;
1255
1256                if (de->d_name[0] == '.')
1257                        continue;
1258                if (ends_with(de->d_name, ".lock"))
1259                        continue;
1260                strbuf_addstr(&refname, de->d_name);
1261                strbuf_addstr(&path, de->d_name);
1262                if (stat(path.buf, &st) < 0) {
1263                        ; /* silently ignore */
1264                } else if (S_ISDIR(st.st_mode)) {
1265                        strbuf_addch(&refname, '/');
1266                        add_entry_to_dir(dir,
1267                                         create_dir_entry(refs, refname.buf,
1268                                                          refname.len, 1));
1269                } else {
1270                        if (!resolve_ref_recursively(&refs->base,
1271                                                     refname.buf,
1272                                                     RESOLVE_REF_READING,
1273                                                     sha1, &flag)) {
1274                                hashclr(sha1);
1275                                flag |= REF_ISBROKEN;
1276                        } else if (is_null_sha1(sha1)) {
1277                                /*
1278                                 * It is so astronomically unlikely
1279                                 * that NULL_SHA1 is the SHA-1 of an
1280                                 * actual object that we consider its
1281                                 * appearance in a loose reference
1282                                 * file to be repo corruption
1283                                 * (probably due to a software bug).
1284                                 */
1285                                flag |= REF_ISBROKEN;
1286                        }
1287
1288                        if (check_refname_format(refname.buf,
1289                                                 REFNAME_ALLOW_ONELEVEL)) {
1290                                if (!refname_is_safe(refname.buf))
1291                                        die("loose refname is dangerous: %s", refname.buf);
1292                                hashclr(sha1);
1293                                flag |= REF_BAD_NAME | REF_ISBROKEN;
1294                        }
1295                        add_entry_to_dir(dir,
1296                                         create_ref_entry(refname.buf, sha1, flag, 0));
1297                }
1298                strbuf_setlen(&refname, dirnamelen);
1299                strbuf_setlen(&path, path_baselen);
1300        }
1301        strbuf_release(&refname);
1302        strbuf_release(&path);
1303        closedir(d);
1304}
1305
1306static struct ref_dir *get_loose_refs(struct files_ref_store *refs)
1307{
1308        if (!refs->loose) {
1309                /*
1310                 * Mark the top-level directory complete because we
1311                 * are about to read the only subdirectory that can
1312                 * hold references:
1313                 */
1314                refs->loose = create_dir_entry(refs, "", 0, 0);
1315                /*
1316                 * Create an incomplete entry for "refs/":
1317                 */
1318                add_entry_to_dir(get_ref_dir(refs->loose),
1319                                 create_dir_entry(refs, "refs/", 5, 1));
1320        }
1321        return get_ref_dir(refs->loose);
1322}
1323
1324/*
1325 * Return the ref_entry for the given refname from the packed
1326 * references.  If it does not exist, return NULL.
1327 */
1328static struct ref_entry *get_packed_ref(struct files_ref_store *refs,
1329                                        const char *refname)
1330{
1331        return find_ref(get_packed_refs(refs), refname);
1332}
1333
1334/*
1335 * A loose ref file doesn't exist; check for a packed ref.
1336 */
1337static int resolve_packed_ref(struct files_ref_store *refs,
1338                              const char *refname,
1339                              unsigned char *sha1, unsigned int *flags)
1340{
1341        struct ref_entry *entry;
1342
1343        /*
1344         * The loose reference file does not exist; check for a packed
1345         * reference.
1346         */
1347        entry = get_packed_ref(refs, refname);
1348        if (entry) {
1349                hashcpy(sha1, entry->u.value.oid.hash);
1350                *flags |= REF_ISPACKED;
1351                return 0;
1352        }
1353        /* refname is not a packed reference. */
1354        return -1;
1355}
1356
1357static int files_read_raw_ref(struct ref_store *ref_store,
1358                              const char *refname, unsigned char *sha1,
1359                              struct strbuf *referent, unsigned int *type)
1360{
1361        struct files_ref_store *refs =
1362                files_downcast(ref_store, 1, "read_raw_ref");
1363        struct strbuf sb_contents = STRBUF_INIT;
1364        struct strbuf sb_path = STRBUF_INIT;
1365        const char *path;
1366        const char *buf;
1367        struct stat st;
1368        int fd;
1369        int ret = -1;
1370        int save_errno;
1371        int remaining_retries = 3;
1372
1373        *type = 0;
1374        strbuf_reset(&sb_path);
1375
1376        if (refs->submodule)
1377                strbuf_git_path_submodule(&sb_path, refs->submodule, "%s", refname);
1378        else
1379                strbuf_git_path(&sb_path, "%s", refname);
1380
1381        path = sb_path.buf;
1382
1383stat_ref:
1384        /*
1385         * We might have to loop back here to avoid a race
1386         * condition: first we lstat() the file, then we try
1387         * to read it as a link or as a file.  But if somebody
1388         * changes the type of the file (file <-> directory
1389         * <-> symlink) between the lstat() and reading, then
1390         * we don't want to report that as an error but rather
1391         * try again starting with the lstat().
1392         *
1393         * We'll keep a count of the retries, though, just to avoid
1394         * any confusing situation sending us into an infinite loop.
1395         */
1396
1397        if (remaining_retries-- <= 0)
1398                goto out;
1399
1400        if (lstat(path, &st) < 0) {
1401                if (errno != ENOENT)
1402                        goto out;
1403                if (resolve_packed_ref(refs, refname, sha1, type)) {
1404                        errno = ENOENT;
1405                        goto out;
1406                }
1407                ret = 0;
1408                goto out;
1409        }
1410
1411        /* Follow "normalized" - ie "refs/.." symlinks by hand */
1412        if (S_ISLNK(st.st_mode)) {
1413                strbuf_reset(&sb_contents);
1414                if (strbuf_readlink(&sb_contents, path, 0) < 0) {
1415                        if (errno == ENOENT || errno == EINVAL)
1416                                /* inconsistent with lstat; retry */
1417                                goto stat_ref;
1418                        else
1419                                goto out;
1420                }
1421                if (starts_with(sb_contents.buf, "refs/") &&
1422                    !check_refname_format(sb_contents.buf, 0)) {
1423                        strbuf_swap(&sb_contents, referent);
1424                        *type |= REF_ISSYMREF;
1425                        ret = 0;
1426                        goto out;
1427                }
1428                /*
1429                 * It doesn't look like a refname; fall through to just
1430                 * treating it like a non-symlink, and reading whatever it
1431                 * points to.
1432                 */
1433        }
1434
1435        /* Is it a directory? */
1436        if (S_ISDIR(st.st_mode)) {
1437                /*
1438                 * Even though there is a directory where the loose
1439                 * ref is supposed to be, there could still be a
1440                 * packed ref:
1441                 */
1442                if (resolve_packed_ref(refs, refname, sha1, type)) {
1443                        errno = EISDIR;
1444                        goto out;
1445                }
1446                ret = 0;
1447                goto out;
1448        }
1449
1450        /*
1451         * Anything else, just open it and try to use it as
1452         * a ref
1453         */
1454        fd = open(path, O_RDONLY);
1455        if (fd < 0) {
1456                if (errno == ENOENT && !S_ISLNK(st.st_mode))
1457                        /* inconsistent with lstat; retry */
1458                        goto stat_ref;
1459                else
1460                        goto out;
1461        }
1462        strbuf_reset(&sb_contents);
1463        if (strbuf_read(&sb_contents, fd, 256) < 0) {
1464                int save_errno = errno;
1465                close(fd);
1466                errno = save_errno;
1467                goto out;
1468        }
1469        close(fd);
1470        strbuf_rtrim(&sb_contents);
1471        buf = sb_contents.buf;
1472        if (starts_with(buf, "ref:")) {
1473                buf += 4;
1474                while (isspace(*buf))
1475                        buf++;
1476
1477                strbuf_reset(referent);
1478                strbuf_addstr(referent, buf);
1479                *type |= REF_ISSYMREF;
1480                ret = 0;
1481                goto out;
1482        }
1483
1484        /*
1485         * Please note that FETCH_HEAD has additional
1486         * data after the sha.
1487         */
1488        if (get_sha1_hex(buf, sha1) ||
1489            (buf[40] != '\0' && !isspace(buf[40]))) {
1490                *type |= REF_ISBROKEN;
1491                errno = EINVAL;
1492                goto out;
1493        }
1494
1495        ret = 0;
1496
1497out:
1498        save_errno = errno;
1499        strbuf_release(&sb_path);
1500        strbuf_release(&sb_contents);
1501        errno = save_errno;
1502        return ret;
1503}
1504
1505static void unlock_ref(struct ref_lock *lock)
1506{
1507        /* Do not free lock->lk -- atexit() still looks at them */
1508        if (lock->lk)
1509                rollback_lock_file(lock->lk);
1510        free(lock->ref_name);
1511        free(lock);
1512}
1513
1514/*
1515 * Lock refname, without following symrefs, and set *lock_p to point
1516 * at a newly-allocated lock object. Fill in lock->old_oid, referent,
1517 * and type similarly to read_raw_ref().
1518 *
1519 * The caller must verify that refname is a "safe" reference name (in
1520 * the sense of refname_is_safe()) before calling this function.
1521 *
1522 * If the reference doesn't already exist, verify that refname doesn't
1523 * have a D/F conflict with any existing references. extras and skip
1524 * are passed to verify_refname_available_dir() for this check.
1525 *
1526 * If mustexist is not set and the reference is not found or is
1527 * broken, lock the reference anyway but clear sha1.
1528 *
1529 * Return 0 on success. On failure, write an error message to err and
1530 * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
1531 *
1532 * Implementation note: This function is basically
1533 *
1534 *     lock reference
1535 *     read_raw_ref()
1536 *
1537 * but it includes a lot more code to
1538 * - Deal with possible races with other processes
1539 * - Avoid calling verify_refname_available_dir() when it can be
1540 *   avoided, namely if we were successfully able to read the ref
1541 * - Generate informative error messages in the case of failure
1542 */
1543static int lock_raw_ref(struct files_ref_store *refs,
1544                        const char *refname, int mustexist,
1545                        const struct string_list *extras,
1546                        const struct string_list *skip,
1547                        struct ref_lock **lock_p,
1548                        struct strbuf *referent,
1549                        unsigned int *type,
1550                        struct strbuf *err)
1551{
1552        struct ref_lock *lock;
1553        struct strbuf ref_file = STRBUF_INIT;
1554        int attempts_remaining = 3;
1555        int ret = TRANSACTION_GENERIC_ERROR;
1556
1557        assert(err);
1558        files_assert_main_repository(refs, "lock_raw_ref");
1559
1560        *type = 0;
1561
1562        /* First lock the file so it can't change out from under us. */
1563
1564        *lock_p = lock = xcalloc(1, sizeof(*lock));
1565
1566        lock->ref_name = xstrdup(refname);
1567        strbuf_git_path(&ref_file, "%s", refname);
1568
1569retry:
1570        switch (safe_create_leading_directories(ref_file.buf)) {
1571        case SCLD_OK:
1572                break; /* success */
1573        case SCLD_EXISTS:
1574                /*
1575                 * Suppose refname is "refs/foo/bar". We just failed
1576                 * to create the containing directory, "refs/foo",
1577                 * because there was a non-directory in the way. This
1578                 * indicates a D/F conflict, probably because of
1579                 * another reference such as "refs/foo". There is no
1580                 * reason to expect this error to be transitory.
1581                 */
1582                if (verify_refname_available(refname, extras, skip, err)) {
1583                        if (mustexist) {
1584                                /*
1585                                 * To the user the relevant error is
1586                                 * that the "mustexist" reference is
1587                                 * missing:
1588                                 */
1589                                strbuf_reset(err);
1590                                strbuf_addf(err, "unable to resolve reference '%s'",
1591                                            refname);
1592                        } else {
1593                                /*
1594                                 * The error message set by
1595                                 * verify_refname_available_dir() is OK.
1596                                 */
1597                                ret = TRANSACTION_NAME_CONFLICT;
1598                        }
1599                } else {
1600                        /*
1601                         * The file that is in the way isn't a loose
1602                         * reference. Report it as a low-level
1603                         * failure.
1604                         */
1605                        strbuf_addf(err, "unable to create lock file %s.lock; "
1606                                    "non-directory in the way",
1607                                    ref_file.buf);
1608                }
1609                goto error_return;
1610        case SCLD_VANISHED:
1611                /* Maybe another process was tidying up. Try again. */
1612                if (--attempts_remaining > 0)
1613                        goto retry;
1614                /* fall through */
1615        default:
1616                strbuf_addf(err, "unable to create directory for %s",
1617                            ref_file.buf);
1618                goto error_return;
1619        }
1620
1621        if (!lock->lk)
1622                lock->lk = xcalloc(1, sizeof(struct lock_file));
1623
1624        if (hold_lock_file_for_update(lock->lk, ref_file.buf, LOCK_NO_DEREF) < 0) {
1625                if (errno == ENOENT && --attempts_remaining > 0) {
1626                        /*
1627                         * Maybe somebody just deleted one of the
1628                         * directories leading to ref_file.  Try
1629                         * again:
1630                         */
1631                        goto retry;
1632                } else {
1633                        unable_to_lock_message(ref_file.buf, errno, err);
1634                        goto error_return;
1635                }
1636        }
1637
1638        /*
1639         * Now we hold the lock and can read the reference without
1640         * fear that its value will change.
1641         */
1642
1643        if (files_read_raw_ref(&refs->base, refname,
1644                               lock->old_oid.hash, referent, type)) {
1645                if (errno == ENOENT) {
1646                        if (mustexist) {
1647                                /* Garden variety missing reference. */
1648                                strbuf_addf(err, "unable to resolve reference '%s'",
1649                                            refname);
1650                                goto error_return;
1651                        } else {
1652                                /*
1653                                 * Reference is missing, but that's OK. We
1654                                 * know that there is not a conflict with
1655                                 * another loose reference because
1656                                 * (supposing that we are trying to lock
1657                                 * reference "refs/foo/bar"):
1658                                 *
1659                                 * - We were successfully able to create
1660                                 *   the lockfile refs/foo/bar.lock, so we
1661                                 *   know there cannot be a loose reference
1662                                 *   named "refs/foo".
1663                                 *
1664                                 * - We got ENOENT and not EISDIR, so we
1665                                 *   know that there cannot be a loose
1666                                 *   reference named "refs/foo/bar/baz".
1667                                 */
1668                        }
1669                } else if (errno == EISDIR) {
1670                        /*
1671                         * There is a directory in the way. It might have
1672                         * contained references that have been deleted. If
1673                         * we don't require that the reference already
1674                         * exists, try to remove the directory so that it
1675                         * doesn't cause trouble when we want to rename the
1676                         * lockfile into place later.
1677                         */
1678                        if (mustexist) {
1679                                /* Garden variety missing reference. */
1680                                strbuf_addf(err, "unable to resolve reference '%s'",
1681                                            refname);
1682                                goto error_return;
1683                        } else if (remove_dir_recursively(&ref_file,
1684                                                          REMOVE_DIR_EMPTY_ONLY)) {
1685                                if (verify_refname_available_dir(
1686                                                    refname, extras, skip,
1687                                                    get_loose_refs(refs),
1688                                                    err)) {
1689                                        /*
1690                                         * The error message set by
1691                                         * verify_refname_available() is OK.
1692                                         */
1693                                        ret = TRANSACTION_NAME_CONFLICT;
1694                                        goto error_return;
1695                                } else {
1696                                        /*
1697                                         * We can't delete the directory,
1698                                         * but we also don't know of any
1699                                         * references that it should
1700                                         * contain.
1701                                         */
1702                                        strbuf_addf(err, "there is a non-empty directory '%s' "
1703                                                    "blocking reference '%s'",
1704                                                    ref_file.buf, refname);
1705                                        goto error_return;
1706                                }
1707                        }
1708                } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
1709                        strbuf_addf(err, "unable to resolve reference '%s': "
1710                                    "reference broken", refname);
1711                        goto error_return;
1712                } else {
1713                        strbuf_addf(err, "unable to resolve reference '%s': %s",
1714                                    refname, strerror(errno));
1715                        goto error_return;
1716                }
1717
1718                /*
1719                 * If the ref did not exist and we are creating it,
1720                 * make sure there is no existing packed ref whose
1721                 * name begins with our refname, nor a packed ref
1722                 * whose name is a proper prefix of our refname.
1723                 */
1724                if (verify_refname_available_dir(
1725                                    refname, extras, skip,
1726                                    get_packed_refs(refs),
1727                                    err)) {
1728                        goto error_return;
1729                }
1730        }
1731
1732        ret = 0;
1733        goto out;
1734
1735error_return:
1736        unlock_ref(lock);
1737        *lock_p = NULL;
1738
1739out:
1740        strbuf_release(&ref_file);
1741        return ret;
1742}
1743
1744/*
1745 * Peel the entry (if possible) and return its new peel_status.  If
1746 * repeel is true, re-peel the entry even if there is an old peeled
1747 * value that is already stored in it.
1748 *
1749 * It is OK to call this function with a packed reference entry that
1750 * might be stale and might even refer to an object that has since
1751 * been garbage-collected.  In such a case, if the entry has
1752 * REF_KNOWS_PEELED then leave the status unchanged and return
1753 * PEEL_PEELED or PEEL_NON_TAG; otherwise, return PEEL_INVALID.
1754 */
1755static enum peel_status peel_entry(struct ref_entry *entry, int repeel)
1756{
1757        enum peel_status status;
1758
1759        if (entry->flag & REF_KNOWS_PEELED) {
1760                if (repeel) {
1761                        entry->flag &= ~REF_KNOWS_PEELED;
1762                        oidclr(&entry->u.value.peeled);
1763                } else {
1764                        return is_null_oid(&entry->u.value.peeled) ?
1765                                PEEL_NON_TAG : PEEL_PEELED;
1766                }
1767        }
1768        if (entry->flag & REF_ISBROKEN)
1769                return PEEL_BROKEN;
1770        if (entry->flag & REF_ISSYMREF)
1771                return PEEL_IS_SYMREF;
1772
1773        status = peel_object(entry->u.value.oid.hash, entry->u.value.peeled.hash);
1774        if (status == PEEL_PEELED || status == PEEL_NON_TAG)
1775                entry->flag |= REF_KNOWS_PEELED;
1776        return status;
1777}
1778
1779static int files_peel_ref(struct ref_store *ref_store,
1780                          const char *refname, unsigned char *sha1)
1781{
1782        struct files_ref_store *refs = files_downcast(ref_store, 0, "peel_ref");
1783        int flag;
1784        unsigned char base[20];
1785
1786        if (current_ref_iter && current_ref_iter->refname == refname) {
1787                struct object_id peeled;
1788
1789                if (ref_iterator_peel(current_ref_iter, &peeled))
1790                        return -1;
1791                hashcpy(sha1, peeled.hash);
1792                return 0;
1793        }
1794
1795        if (read_ref_full(refname, RESOLVE_REF_READING, base, &flag))
1796                return -1;
1797
1798        /*
1799         * If the reference is packed, read its ref_entry from the
1800         * cache in the hope that we already know its peeled value.
1801         * We only try this optimization on packed references because
1802         * (a) forcing the filling of the loose reference cache could
1803         * be expensive and (b) loose references anyway usually do not
1804         * have REF_KNOWS_PEELED.
1805         */
1806        if (flag & REF_ISPACKED) {
1807                struct ref_entry *r = get_packed_ref(refs, refname);
1808                if (r) {
1809                        if (peel_entry(r, 0))
1810                                return -1;
1811                        hashcpy(sha1, r->u.value.peeled.hash);
1812                        return 0;
1813                }
1814        }
1815
1816        return peel_object(base, sha1);
1817}
1818
1819struct files_ref_iterator {
1820        struct ref_iterator base;
1821
1822        struct packed_ref_cache *packed_ref_cache;
1823        struct ref_iterator *iter0;
1824        unsigned int flags;
1825};
1826
1827static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
1828{
1829        struct files_ref_iterator *iter =
1830                (struct files_ref_iterator *)ref_iterator;
1831        int ok;
1832
1833        while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
1834                if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
1835                    ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
1836                        continue;
1837
1838                if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
1839                    !ref_resolves_to_object(iter->iter0->refname,
1840                                            iter->iter0->oid,
1841                                            iter->iter0->flags))
1842                        continue;
1843
1844                iter->base.refname = iter->iter0->refname;
1845                iter->base.oid = iter->iter0->oid;
1846                iter->base.flags = iter->iter0->flags;
1847                return ITER_OK;
1848        }
1849
1850        iter->iter0 = NULL;
1851        if (ref_iterator_abort(ref_iterator) != ITER_DONE)
1852                ok = ITER_ERROR;
1853
1854        return ok;
1855}
1856
1857static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
1858                                   struct object_id *peeled)
1859{
1860        struct files_ref_iterator *iter =
1861                (struct files_ref_iterator *)ref_iterator;
1862
1863        return ref_iterator_peel(iter->iter0, peeled);
1864}
1865
1866static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
1867{
1868        struct files_ref_iterator *iter =
1869                (struct files_ref_iterator *)ref_iterator;
1870        int ok = ITER_DONE;
1871
1872        if (iter->iter0)
1873                ok = ref_iterator_abort(iter->iter0);
1874
1875        release_packed_ref_cache(iter->packed_ref_cache);
1876        base_ref_iterator_free(ref_iterator);
1877        return ok;
1878}
1879
1880static struct ref_iterator_vtable files_ref_iterator_vtable = {
1881        files_ref_iterator_advance,
1882        files_ref_iterator_peel,
1883        files_ref_iterator_abort
1884};
1885
1886static struct ref_iterator *files_ref_iterator_begin(
1887                struct ref_store *ref_store,
1888                const char *prefix, unsigned int flags)
1889{
1890        struct files_ref_store *refs =
1891                files_downcast(ref_store, 1, "ref_iterator_begin");
1892        struct ref_dir *loose_dir, *packed_dir;
1893        struct ref_iterator *loose_iter, *packed_iter;
1894        struct files_ref_iterator *iter;
1895        struct ref_iterator *ref_iterator;
1896
1897        if (!refs)
1898                return empty_ref_iterator_begin();
1899
1900        if (ref_paranoia < 0)
1901                ref_paranoia = git_env_bool("GIT_REF_PARANOIA", 0);
1902        if (ref_paranoia)
1903                flags |= DO_FOR_EACH_INCLUDE_BROKEN;
1904
1905        iter = xcalloc(1, sizeof(*iter));
1906        ref_iterator = &iter->base;
1907        base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable);
1908
1909        /*
1910         * We must make sure that all loose refs are read before
1911         * accessing the packed-refs file; this avoids a race
1912         * condition if loose refs are migrated to the packed-refs
1913         * file by a simultaneous process, but our in-memory view is
1914         * from before the migration. We ensure this as follows:
1915         * First, we call prime_ref_dir(), which pre-reads the loose
1916         * references for the subtree into the cache. (If they've
1917         * already been read, that's OK; we only need to guarantee
1918         * that they're read before the packed refs, not *how much*
1919         * before.) After that, we call get_packed_ref_cache(), which
1920         * internally checks whether the packed-ref cache is up to
1921         * date with what is on disk, and re-reads it if not.
1922         */
1923
1924        loose_dir = get_loose_refs(refs);
1925
1926        if (prefix && *prefix)
1927                loose_dir = find_containing_dir(loose_dir, prefix, 0);
1928
1929        if (loose_dir) {
1930                prime_ref_dir(loose_dir);
1931                loose_iter = cache_ref_iterator_begin(loose_dir);
1932        } else {
1933                /* There's nothing to iterate over. */
1934                loose_iter = empty_ref_iterator_begin();
1935        }
1936
1937        iter->packed_ref_cache = get_packed_ref_cache(refs);
1938        acquire_packed_ref_cache(iter->packed_ref_cache);
1939        packed_dir = get_packed_ref_dir(iter->packed_ref_cache);
1940
1941        if (prefix && *prefix)
1942                packed_dir = find_containing_dir(packed_dir, prefix, 0);
1943
1944        if (packed_dir) {
1945                packed_iter = cache_ref_iterator_begin(packed_dir);
1946        } else {
1947                /* There's nothing to iterate over. */
1948                packed_iter = empty_ref_iterator_begin();
1949        }
1950
1951        iter->iter0 = overlay_ref_iterator_begin(loose_iter, packed_iter);
1952        iter->flags = flags;
1953
1954        return ref_iterator;
1955}
1956
1957/*
1958 * Verify that the reference locked by lock has the value old_sha1.
1959 * Fail if the reference doesn't exist and mustexist is set. Return 0
1960 * on success. On error, write an error message to err, set errno, and
1961 * return a negative value.
1962 */
1963static int verify_lock(struct ref_lock *lock,
1964                       const unsigned char *old_sha1, int mustexist,
1965                       struct strbuf *err)
1966{
1967        assert(err);
1968
1969        if (read_ref_full(lock->ref_name,
1970                          mustexist ? RESOLVE_REF_READING : 0,
1971                          lock->old_oid.hash, NULL)) {
1972                if (old_sha1) {
1973                        int save_errno = errno;
1974                        strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
1975                        errno = save_errno;
1976                        return -1;
1977                } else {
1978                        oidclr(&lock->old_oid);
1979                        return 0;
1980                }
1981        }
1982        if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
1983                strbuf_addf(err, "ref '%s' is at %s but expected %s",
1984                            lock->ref_name,
1985                            oid_to_hex(&lock->old_oid),
1986                            sha1_to_hex(old_sha1));
1987                errno = EBUSY;
1988                return -1;
1989        }
1990        return 0;
1991}
1992
1993static int remove_empty_directories(struct strbuf *path)
1994{
1995        /*
1996         * we want to create a file but there is a directory there;
1997         * if that is an empty directory (or a directory that contains
1998         * only empty directories), remove them.
1999         */
2000        return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
2001}
2002
2003static int create_reflock(const char *path, void *cb)
2004{
2005        struct lock_file *lk = cb;
2006
2007        return hold_lock_file_for_update(lk, path, LOCK_NO_DEREF) < 0 ? -1 : 0;
2008}
2009
2010/*
2011 * Locks a ref returning the lock on success and NULL on failure.
2012 * On failure errno is set to something meaningful.
2013 */
2014static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
2015                                            const char *refname,
2016                                            const unsigned char *old_sha1,
2017                                            const struct string_list *extras,
2018                                            const struct string_list *skip,
2019                                            unsigned int flags, int *type,
2020                                            struct strbuf *err)
2021{
2022        struct strbuf ref_file = STRBUF_INIT;
2023        struct ref_lock *lock;
2024        int last_errno = 0;
2025        int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
2026        int resolve_flags = RESOLVE_REF_NO_RECURSE;
2027        int resolved;
2028
2029        files_assert_main_repository(refs, "lock_ref_sha1_basic");
2030        assert(err);
2031
2032        lock = xcalloc(1, sizeof(struct ref_lock));
2033
2034        if (mustexist)
2035                resolve_flags |= RESOLVE_REF_READING;
2036        if (flags & REF_DELETING)
2037                resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
2038
2039        strbuf_git_path(&ref_file, "%s", refname);
2040        resolved = !!resolve_ref_unsafe(refname, resolve_flags,
2041                                        lock->old_oid.hash, type);
2042        if (!resolved && errno == EISDIR) {
2043                /*
2044                 * we are trying to lock foo but we used to
2045                 * have foo/bar which now does not exist;
2046                 * it is normal for the empty directory 'foo'
2047                 * to remain.
2048                 */
2049                if (remove_empty_directories(&ref_file)) {
2050                        last_errno = errno;
2051                        if (!verify_refname_available_dir(
2052                                            refname, extras, skip,
2053                                            get_loose_refs(refs), err))
2054                                strbuf_addf(err, "there are still refs under '%s'",
2055                                            refname);
2056                        goto error_return;
2057                }
2058                resolved = !!resolve_ref_unsafe(refname, resolve_flags,
2059                                                lock->old_oid.hash, type);
2060        }
2061        if (!resolved) {
2062                last_errno = errno;
2063                if (last_errno != ENOTDIR ||
2064                    !verify_refname_available_dir(
2065                                    refname, extras, skip,
2066                                    get_loose_refs(refs), err))
2067                        strbuf_addf(err, "unable to resolve reference '%s': %s",
2068                                    refname, strerror(last_errno));
2069
2070                goto error_return;
2071        }
2072
2073        /*
2074         * If the ref did not exist and we are creating it, make sure
2075         * there is no existing packed ref whose name begins with our
2076         * refname, nor a packed ref whose name is a proper prefix of
2077         * our refname.
2078         */
2079        if (is_null_oid(&lock->old_oid) &&
2080            verify_refname_available_dir(refname, extras, skip,
2081                                         get_packed_refs(refs),
2082                                         err)) {
2083                last_errno = ENOTDIR;
2084                goto error_return;
2085        }
2086
2087        lock->lk = xcalloc(1, sizeof(struct lock_file));
2088
2089        lock->ref_name = xstrdup(refname);
2090
2091        if (raceproof_create_file(ref_file.buf, create_reflock, lock->lk)) {
2092                last_errno = errno;
2093                unable_to_lock_message(ref_file.buf, errno, err);
2094                goto error_return;
2095        }
2096
2097        if (verify_lock(lock, old_sha1, mustexist, err)) {
2098                last_errno = errno;
2099                goto error_return;
2100        }
2101        goto out;
2102
2103 error_return:
2104        unlock_ref(lock);
2105        lock = NULL;
2106
2107 out:
2108        strbuf_release(&ref_file);
2109        errno = last_errno;
2110        return lock;
2111}
2112
2113/*
2114 * Write an entry to the packed-refs file for the specified refname.
2115 * If peeled is non-NULL, write it as the entry's peeled value.
2116 */
2117static void write_packed_entry(FILE *fh, char *refname, unsigned char *sha1,
2118                               unsigned char *peeled)
2119{
2120        fprintf_or_die(fh, "%s %s\n", sha1_to_hex(sha1), refname);
2121        if (peeled)
2122                fprintf_or_die(fh, "^%s\n", sha1_to_hex(peeled));
2123}
2124
2125/*
2126 * An each_ref_entry_fn that writes the entry to a packed-refs file.
2127 */
2128static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
2129{
2130        enum peel_status peel_status = peel_entry(entry, 0);
2131
2132        if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
2133                error("internal error: %s is not a valid packed reference!",
2134                      entry->name);
2135        write_packed_entry(cb_data, entry->name, entry->u.value.oid.hash,
2136                           peel_status == PEEL_PEELED ?
2137                           entry->u.value.peeled.hash : NULL);
2138        return 0;
2139}
2140
2141/*
2142 * Lock the packed-refs file for writing. Flags is passed to
2143 * hold_lock_file_for_update(). Return 0 on success. On errors, set
2144 * errno appropriately and return a nonzero value.
2145 */
2146static int lock_packed_refs(struct files_ref_store *refs, int flags)
2147{
2148        static int timeout_configured = 0;
2149        static int timeout_value = 1000;
2150        struct packed_ref_cache *packed_ref_cache;
2151
2152        files_assert_main_repository(refs, "lock_packed_refs");
2153
2154        if (!timeout_configured) {
2155                git_config_get_int("core.packedrefstimeout", &timeout_value);
2156                timeout_configured = 1;
2157        }
2158
2159        if (hold_lock_file_for_update_timeout(
2160                            &packlock, git_path("packed-refs"),
2161                            flags, timeout_value) < 0)
2162                return -1;
2163        /*
2164         * Get the current packed-refs while holding the lock.  If the
2165         * packed-refs file has been modified since we last read it,
2166         * this will automatically invalidate the cache and re-read
2167         * the packed-refs file.
2168         */
2169        packed_ref_cache = get_packed_ref_cache(refs);
2170        packed_ref_cache->lock = &packlock;
2171        /* Increment the reference count to prevent it from being freed: */
2172        acquire_packed_ref_cache(packed_ref_cache);
2173        return 0;
2174}
2175
2176/*
2177 * Write the current version of the packed refs cache from memory to
2178 * disk. The packed-refs file must already be locked for writing (see
2179 * lock_packed_refs()). Return zero on success. On errors, set errno
2180 * and return a nonzero value
2181 */
2182static int commit_packed_refs(struct files_ref_store *refs)
2183{
2184        struct packed_ref_cache *packed_ref_cache =
2185                get_packed_ref_cache(refs);
2186        int error = 0;
2187        int save_errno = 0;
2188        FILE *out;
2189
2190        files_assert_main_repository(refs, "commit_packed_refs");
2191
2192        if (!packed_ref_cache->lock)
2193                die("internal error: packed-refs not locked");
2194
2195        out = fdopen_lock_file(packed_ref_cache->lock, "w");
2196        if (!out)
2197                die_errno("unable to fdopen packed-refs descriptor");
2198
2199        fprintf_or_die(out, "%s", PACKED_REFS_HEADER);
2200        do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
2201                                 0, write_packed_entry_fn, out);
2202
2203        if (commit_lock_file(packed_ref_cache->lock)) {
2204                save_errno = errno;
2205                error = -1;
2206        }
2207        packed_ref_cache->lock = NULL;
2208        release_packed_ref_cache(packed_ref_cache);
2209        errno = save_errno;
2210        return error;
2211}
2212
2213/*
2214 * Rollback the lockfile for the packed-refs file, and discard the
2215 * in-memory packed reference cache.  (The packed-refs file will be
2216 * read anew if it is needed again after this function is called.)
2217 */
2218static void rollback_packed_refs(struct files_ref_store *refs)
2219{
2220        struct packed_ref_cache *packed_ref_cache =
2221                get_packed_ref_cache(refs);
2222
2223        files_assert_main_repository(refs, "rollback_packed_refs");
2224
2225        if (!packed_ref_cache->lock)
2226                die("internal error: packed-refs not locked");
2227        rollback_lock_file(packed_ref_cache->lock);
2228        packed_ref_cache->lock = NULL;
2229        release_packed_ref_cache(packed_ref_cache);
2230        clear_packed_ref_cache(refs);
2231}
2232
2233struct ref_to_prune {
2234        struct ref_to_prune *next;
2235        unsigned char sha1[20];
2236        char name[FLEX_ARRAY];
2237};
2238
2239struct pack_refs_cb_data {
2240        unsigned int flags;
2241        struct ref_dir *packed_refs;
2242        struct ref_to_prune *ref_to_prune;
2243};
2244
2245/*
2246 * An each_ref_entry_fn that is run over loose references only.  If
2247 * the loose reference can be packed, add an entry in the packed ref
2248 * cache.  If the reference should be pruned, also add it to
2249 * ref_to_prune in the pack_refs_cb_data.
2250 */
2251static int pack_if_possible_fn(struct ref_entry *entry, void *cb_data)
2252{
2253        struct pack_refs_cb_data *cb = cb_data;
2254        enum peel_status peel_status;
2255        struct ref_entry *packed_entry;
2256        int is_tag_ref = starts_with(entry->name, "refs/tags/");
2257
2258        /* Do not pack per-worktree refs: */
2259        if (ref_type(entry->name) != REF_TYPE_NORMAL)
2260                return 0;
2261
2262        /* ALWAYS pack tags */
2263        if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref)
2264                return 0;
2265
2266        /* Do not pack symbolic or broken refs: */
2267        if ((entry->flag & REF_ISSYMREF) || !entry_resolves_to_object(entry))
2268                return 0;
2269
2270        /* Add a packed ref cache entry equivalent to the loose entry. */
2271        peel_status = peel_entry(entry, 1);
2272        if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
2273                die("internal error peeling reference %s (%s)",
2274                    entry->name, oid_to_hex(&entry->u.value.oid));
2275        packed_entry = find_ref(cb->packed_refs, entry->name);
2276        if (packed_entry) {
2277                /* Overwrite existing packed entry with info from loose entry */
2278                packed_entry->flag = REF_ISPACKED | REF_KNOWS_PEELED;
2279                oidcpy(&packed_entry->u.value.oid, &entry->u.value.oid);
2280        } else {
2281                packed_entry = create_ref_entry(entry->name, entry->u.value.oid.hash,
2282                                                REF_ISPACKED | REF_KNOWS_PEELED, 0);
2283                add_ref(cb->packed_refs, packed_entry);
2284        }
2285        oidcpy(&packed_entry->u.value.peeled, &entry->u.value.peeled);
2286
2287        /* Schedule the loose reference for pruning if requested. */
2288        if ((cb->flags & PACK_REFS_PRUNE)) {
2289                struct ref_to_prune *n;
2290                FLEX_ALLOC_STR(n, name, entry->name);
2291                hashcpy(n->sha1, entry->u.value.oid.hash);
2292                n->next = cb->ref_to_prune;
2293                cb->ref_to_prune = n;
2294        }
2295        return 0;
2296}
2297
2298enum {
2299        REMOVE_EMPTY_PARENTS_REF = 0x01,
2300        REMOVE_EMPTY_PARENTS_REFLOG = 0x02
2301};
2302
2303/*
2304 * Remove empty parent directories associated with the specified
2305 * reference and/or its reflog, but spare [logs/]refs/ and immediate
2306 * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
2307 * REMOVE_EMPTY_PARENTS_REFLOG.
2308 */
2309static void try_remove_empty_parents(const char *refname, unsigned int flags)
2310{
2311        struct strbuf buf = STRBUF_INIT;
2312        char *p, *q;
2313        int i;
2314
2315        strbuf_addstr(&buf, refname);
2316        p = buf.buf;
2317        for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
2318                while (*p && *p != '/')
2319                        p++;
2320                /* tolerate duplicate slashes; see check_refname_format() */
2321                while (*p == '/')
2322                        p++;
2323        }
2324        q = buf.buf + buf.len;
2325        while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
2326                while (q > p && *q != '/')
2327                        q--;
2328                while (q > p && *(q-1) == '/')
2329                        q--;
2330                if (q == p)
2331                        break;
2332                strbuf_setlen(&buf, q - buf.buf);
2333                if ((flags & REMOVE_EMPTY_PARENTS_REF) &&
2334                    rmdir(git_path("%s", buf.buf)))
2335                        flags &= ~REMOVE_EMPTY_PARENTS_REF;
2336                if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) &&
2337                    rmdir(git_path("logs/%s", buf.buf)))
2338                        flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
2339        }
2340        strbuf_release(&buf);
2341}
2342
2343/* make sure nobody touched the ref, and unlink */
2344static void prune_ref(struct ref_to_prune *r)
2345{
2346        struct ref_transaction *transaction;
2347        struct strbuf err = STRBUF_INIT;
2348
2349        if (check_refname_format(r->name, 0))
2350                return;
2351
2352        transaction = ref_transaction_begin(&err);
2353        if (!transaction ||
2354            ref_transaction_delete(transaction, r->name, r->sha1,
2355                                   REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
2356            ref_transaction_commit(transaction, &err)) {
2357                ref_transaction_free(transaction);
2358                error("%s", err.buf);
2359                strbuf_release(&err);
2360                return;
2361        }
2362        ref_transaction_free(transaction);
2363        strbuf_release(&err);
2364}
2365
2366static void prune_refs(struct ref_to_prune *r)
2367{
2368        while (r) {
2369                prune_ref(r);
2370                r = r->next;
2371        }
2372}
2373
2374static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
2375{
2376        struct files_ref_store *refs =
2377                files_downcast(ref_store, 0, "pack_refs");
2378        struct pack_refs_cb_data cbdata;
2379
2380        memset(&cbdata, 0, sizeof(cbdata));
2381        cbdata.flags = flags;
2382
2383        lock_packed_refs(refs, LOCK_DIE_ON_ERROR);
2384        cbdata.packed_refs = get_packed_refs(refs);
2385
2386        do_for_each_entry_in_dir(get_loose_refs(refs), 0,
2387                                 pack_if_possible_fn, &cbdata);
2388
2389        if (commit_packed_refs(refs))
2390                die_errno("unable to overwrite old ref-pack file");
2391
2392        prune_refs(cbdata.ref_to_prune);
2393        return 0;
2394}
2395
2396/*
2397 * Rewrite the packed-refs file, omitting any refs listed in
2398 * 'refnames'. On error, leave packed-refs unchanged, write an error
2399 * message to 'err', and return a nonzero value.
2400 *
2401 * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
2402 */
2403static int repack_without_refs(struct files_ref_store *refs,
2404                               struct string_list *refnames, struct strbuf *err)
2405{
2406        struct ref_dir *packed;
2407        struct string_list_item *refname;
2408        int ret, needs_repacking = 0, removed = 0;
2409
2410        files_assert_main_repository(refs, "repack_without_refs");
2411        assert(err);
2412
2413        /* Look for a packed ref */
2414        for_each_string_list_item(refname, refnames) {
2415                if (get_packed_ref(refs, refname->string)) {
2416                        needs_repacking = 1;
2417                        break;
2418                }
2419        }
2420
2421        /* Avoid locking if we have nothing to do */
2422        if (!needs_repacking)
2423                return 0; /* no refname exists in packed refs */
2424
2425        if (lock_packed_refs(refs, 0)) {
2426                unable_to_lock_message(git_path("packed-refs"), errno, err);
2427                return -1;
2428        }
2429        packed = get_packed_refs(refs);
2430
2431        /* Remove refnames from the cache */
2432        for_each_string_list_item(refname, refnames)
2433                if (remove_entry(packed, refname->string) != -1)
2434                        removed = 1;
2435        if (!removed) {
2436                /*
2437                 * All packed entries disappeared while we were
2438                 * acquiring the lock.
2439                 */
2440                rollback_packed_refs(refs);
2441                return 0;
2442        }
2443
2444        /* Write what remains */
2445        ret = commit_packed_refs(refs);
2446        if (ret)
2447                strbuf_addf(err, "unable to overwrite old ref-pack file: %s",
2448                            strerror(errno));
2449        return ret;
2450}
2451
2452static int files_delete_refs(struct ref_store *ref_store,
2453                             struct string_list *refnames, unsigned int flags)
2454{
2455        struct files_ref_store *refs =
2456                files_downcast(ref_store, 0, "delete_refs");
2457        struct strbuf err = STRBUF_INIT;
2458        int i, result = 0;
2459
2460        if (!refnames->nr)
2461                return 0;
2462
2463        result = repack_without_refs(refs, refnames, &err);
2464        if (result) {
2465                /*
2466                 * If we failed to rewrite the packed-refs file, then
2467                 * it is unsafe to try to remove loose refs, because
2468                 * doing so might expose an obsolete packed value for
2469                 * a reference that might even point at an object that
2470                 * has been garbage collected.
2471                 */
2472                if (refnames->nr == 1)
2473                        error(_("could not delete reference %s: %s"),
2474                              refnames->items[0].string, err.buf);
2475                else
2476                        error(_("could not delete references: %s"), err.buf);
2477
2478                goto out;
2479        }
2480
2481        for (i = 0; i < refnames->nr; i++) {
2482                const char *refname = refnames->items[i].string;
2483
2484                if (delete_ref(NULL, refname, NULL, flags))
2485                        result |= error(_("could not remove reference %s"), refname);
2486        }
2487
2488out:
2489        strbuf_release(&err);
2490        return result;
2491}
2492
2493/*
2494 * People using contrib's git-new-workdir have .git/logs/refs ->
2495 * /some/other/path/.git/logs/refs, and that may live on another device.
2496 *
2497 * IOW, to avoid cross device rename errors, the temporary renamed log must
2498 * live into logs/refs.
2499 */
2500#define TMP_RENAMED_LOG  "logs/refs/.tmp-renamed-log"
2501
2502static int rename_tmp_log_callback(const char *path, void *cb)
2503{
2504        int *true_errno = cb;
2505
2506        if (rename(git_path(TMP_RENAMED_LOG), path)) {
2507                /*
2508                 * rename(a, b) when b is an existing directory ought
2509                 * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
2510                 * Sheesh. Record the true errno for error reporting,
2511                 * but report EISDIR to raceproof_create_file() so
2512                 * that it knows to retry.
2513                 */
2514                *true_errno = errno;
2515                if (errno == ENOTDIR)
2516                        errno = EISDIR;
2517                return -1;
2518        } else {
2519                return 0;
2520        }
2521}
2522
2523static int rename_tmp_log(const char *newrefname)
2524{
2525        char *path = git_pathdup("logs/%s", newrefname);
2526        int ret, true_errno;
2527
2528        ret = raceproof_create_file(path, rename_tmp_log_callback, &true_errno);
2529        if (ret) {
2530                if (errno == EISDIR)
2531                        error("directory not empty: %s", path);
2532                else
2533                        error("unable to move logfile %s to %s: %s",
2534                              git_path(TMP_RENAMED_LOG), path,
2535                              strerror(true_errno));
2536        }
2537
2538        free(path);
2539        return ret;
2540}
2541
2542static int files_verify_refname_available(struct ref_store *ref_store,
2543                                          const char *newname,
2544                                          const struct string_list *extras,
2545                                          const struct string_list *skip,
2546                                          struct strbuf *err)
2547{
2548        struct files_ref_store *refs =
2549                files_downcast(ref_store, 1, "verify_refname_available");
2550        struct ref_dir *packed_refs = get_packed_refs(refs);
2551        struct ref_dir *loose_refs = get_loose_refs(refs);
2552
2553        if (verify_refname_available_dir(newname, extras, skip,
2554                                         packed_refs, err) ||
2555            verify_refname_available_dir(newname, extras, skip,
2556                                         loose_refs, err))
2557                return -1;
2558
2559        return 0;
2560}
2561
2562static int write_ref_to_lockfile(struct ref_lock *lock,
2563                                 const unsigned char *sha1, struct strbuf *err);
2564static int commit_ref_update(struct files_ref_store *refs,
2565                             struct ref_lock *lock,
2566                             const unsigned char *sha1, const char *logmsg,
2567                             struct strbuf *err);
2568
2569static int files_rename_ref(struct ref_store *ref_store,
2570                            const char *oldrefname, const char *newrefname,
2571                            const char *logmsg)
2572{
2573        struct files_ref_store *refs =
2574                files_downcast(ref_store, 0, "rename_ref");
2575        unsigned char sha1[20], orig_sha1[20];
2576        int flag = 0, logmoved = 0;
2577        struct ref_lock *lock;
2578        struct stat loginfo;
2579        int log = !lstat(git_path("logs/%s", oldrefname), &loginfo);
2580        struct strbuf err = STRBUF_INIT;
2581
2582        if (log && S_ISLNK(loginfo.st_mode))
2583                return error("reflog for %s is a symlink", oldrefname);
2584
2585        if (!resolve_ref_unsafe(oldrefname, RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
2586                                orig_sha1, &flag))
2587                return error("refname %s not found", oldrefname);
2588
2589        if (flag & REF_ISSYMREF)
2590                return error("refname %s is a symbolic ref, renaming it is not supported",
2591                        oldrefname);
2592        if (!rename_ref_available(oldrefname, newrefname))
2593                return 1;
2594
2595        if (log && rename(git_path("logs/%s", oldrefname), git_path(TMP_RENAMED_LOG)))
2596                return error("unable to move logfile logs/%s to "TMP_RENAMED_LOG": %s",
2597                        oldrefname, strerror(errno));
2598
2599        if (delete_ref(logmsg, oldrefname, orig_sha1, REF_NODEREF)) {
2600                error("unable to delete old %s", oldrefname);
2601                goto rollback;
2602        }
2603
2604        /*
2605         * Since we are doing a shallow lookup, sha1 is not the
2606         * correct value to pass to delete_ref as old_sha1. But that
2607         * doesn't matter, because an old_sha1 check wouldn't add to
2608         * the safety anyway; we want to delete the reference whatever
2609         * its current value.
2610         */
2611        if (!read_ref_full(newrefname, RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
2612                           sha1, NULL) &&
2613            delete_ref(NULL, newrefname, NULL, REF_NODEREF)) {
2614                if (errno == EISDIR) {
2615                        struct strbuf path = STRBUF_INIT;
2616                        int result;
2617
2618                        strbuf_git_path(&path, "%s", newrefname);
2619                        result = remove_empty_directories(&path);
2620                        strbuf_release(&path);
2621
2622                        if (result) {
2623                                error("Directory not empty: %s", newrefname);
2624                                goto rollback;
2625                        }
2626                } else {
2627                        error("unable to delete existing %s", newrefname);
2628                        goto rollback;
2629                }
2630        }
2631
2632        if (log && rename_tmp_log(newrefname))
2633                goto rollback;
2634
2635        logmoved = log;
2636
2637        lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
2638                                   REF_NODEREF, NULL, &err);
2639        if (!lock) {
2640                error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
2641                strbuf_release(&err);
2642                goto rollback;
2643        }
2644        hashcpy(lock->old_oid.hash, orig_sha1);
2645
2646        if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
2647            commit_ref_update(refs, lock, orig_sha1, logmsg, &err)) {
2648                error("unable to write current sha1 into %s: %s", newrefname, err.buf);
2649                strbuf_release(&err);
2650                goto rollback;
2651        }
2652
2653        return 0;
2654
2655 rollback:
2656        lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
2657                                   REF_NODEREF, NULL, &err);
2658        if (!lock) {
2659                error("unable to lock %s for rollback: %s", oldrefname, err.buf);
2660                strbuf_release(&err);
2661                goto rollbacklog;
2662        }
2663
2664        flag = log_all_ref_updates;
2665        log_all_ref_updates = LOG_REFS_NONE;
2666        if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
2667            commit_ref_update(refs, lock, orig_sha1, NULL, &err)) {
2668                error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
2669                strbuf_release(&err);
2670        }
2671        log_all_ref_updates = flag;
2672
2673 rollbacklog:
2674        if (logmoved && rename(git_path("logs/%s", newrefname), git_path("logs/%s", oldrefname)))
2675                error("unable to restore logfile %s from %s: %s",
2676                        oldrefname, newrefname, strerror(errno));
2677        if (!logmoved && log &&
2678            rename(git_path(TMP_RENAMED_LOG), git_path("logs/%s", oldrefname)))
2679                error("unable to restore logfile %s from "TMP_RENAMED_LOG": %s",
2680                        oldrefname, strerror(errno));
2681
2682        return 1;
2683}
2684
2685static int close_ref(struct ref_lock *lock)
2686{
2687        if (close_lock_file(lock->lk))
2688                return -1;
2689        return 0;
2690}
2691
2692static int commit_ref(struct ref_lock *lock)
2693{
2694        char *path = get_locked_file_path(lock->lk);
2695        struct stat st;
2696
2697        if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
2698                /*
2699                 * There is a directory at the path we want to rename
2700                 * the lockfile to. Hopefully it is empty; try to
2701                 * delete it.
2702                 */
2703                size_t len = strlen(path);
2704                struct strbuf sb_path = STRBUF_INIT;
2705
2706                strbuf_attach(&sb_path, path, len, len);
2707
2708                /*
2709                 * If this fails, commit_lock_file() will also fail
2710                 * and will report the problem.
2711                 */
2712                remove_empty_directories(&sb_path);
2713                strbuf_release(&sb_path);
2714        } else {
2715                free(path);
2716        }
2717
2718        if (commit_lock_file(lock->lk))
2719                return -1;
2720        return 0;
2721}
2722
2723static int open_or_create_logfile(const char *path, void *cb)
2724{
2725        int *fd = cb;
2726
2727        *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
2728        return (*fd < 0) ? -1 : 0;
2729}
2730
2731/*
2732 * Create a reflog for a ref. If force_create = 0, only create the
2733 * reflog for certain refs (those for which should_autocreate_reflog
2734 * returns non-zero). Otherwise, create it regardless of the reference
2735 * name. If the logfile already existed or was created, return 0 and
2736 * set *logfd to the file descriptor opened for appending to the file.
2737 * If no logfile exists and we decided not to create one, return 0 and
2738 * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
2739 * return -1.
2740 */
2741static int log_ref_setup(const char *refname, int force_create,
2742                         int *logfd, struct strbuf *err)
2743{
2744        char *logfile = git_pathdup("logs/%s", refname);
2745
2746        if (force_create || should_autocreate_reflog(refname)) {
2747                if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
2748                        if (errno == ENOENT)
2749                                strbuf_addf(err, "unable to create directory for '%s': "
2750                                            "%s", logfile, strerror(errno));
2751                        else if (errno == EISDIR)
2752                                strbuf_addf(err, "there are still logs under '%s'",
2753                                            logfile);
2754                        else
2755                                strbuf_addf(err, "unable to append to '%s': %s",
2756                                            logfile, strerror(errno));
2757
2758                        goto error;
2759                }
2760        } else {
2761                *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
2762                if (*logfd < 0) {
2763                        if (errno == ENOENT || errno == EISDIR) {
2764                                /*
2765                                 * The logfile doesn't already exist,
2766                                 * but that is not an error; it only
2767                                 * means that we won't write log
2768                                 * entries to it.
2769                                 */
2770                                ;
2771                        } else {
2772                                strbuf_addf(err, "unable to append to '%s': %s",
2773                                            logfile, strerror(errno));
2774                                goto error;
2775                        }
2776                }
2777        }
2778
2779        if (*logfd >= 0)
2780                adjust_shared_perm(logfile);
2781
2782        free(logfile);
2783        return 0;
2784
2785error:
2786        free(logfile);
2787        return -1;
2788}
2789
2790static int files_create_reflog(struct ref_store *ref_store,
2791                               const char *refname, int force_create,
2792                               struct strbuf *err)
2793{
2794        int fd;
2795
2796        /* Check validity (but we don't need the result): */
2797        files_downcast(ref_store, 0, "create_reflog");
2798
2799        if (log_ref_setup(refname, force_create, &fd, err))
2800                return -1;
2801
2802        if (fd >= 0)
2803                close(fd);
2804
2805        return 0;
2806}
2807
2808static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
2809                            const unsigned char *new_sha1,
2810                            const char *committer, const char *msg)
2811{
2812        int msglen, written;
2813        unsigned maxlen, len;
2814        char *logrec;
2815
2816        msglen = msg ? strlen(msg) : 0;
2817        maxlen = strlen(committer) + msglen + 100;
2818        logrec = xmalloc(maxlen);
2819        len = xsnprintf(logrec, maxlen, "%s %s %s\n",
2820                        sha1_to_hex(old_sha1),
2821                        sha1_to_hex(new_sha1),
2822                        committer);
2823        if (msglen)
2824                len += copy_reflog_msg(logrec + len - 1, msg) - 1;
2825
2826        written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
2827        free(logrec);
2828        if (written != len)
2829                return -1;
2830
2831        return 0;
2832}
2833
2834int files_log_ref_write(const char *refname, const unsigned char *old_sha1,
2835                        const unsigned char *new_sha1, const char *msg,
2836                        int flags, struct strbuf *err)
2837{
2838        int logfd, result;
2839
2840        if (log_all_ref_updates == LOG_REFS_UNSET)
2841                log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
2842
2843        result = log_ref_setup(refname, flags & REF_FORCE_CREATE_REFLOG,
2844                               &logfd, err);
2845
2846        if (result)
2847                return result;
2848
2849        if (logfd < 0)
2850                return 0;
2851        result = log_ref_write_fd(logfd, old_sha1, new_sha1,
2852                                  git_committer_info(0), msg);
2853        if (result) {
2854                int save_errno = errno;
2855
2856                strbuf_addf(err, "unable to append to '%s': %s",
2857                            git_path("logs/%s", refname), strerror(save_errno));
2858                close(logfd);
2859                return -1;
2860        }
2861        if (close(logfd)) {
2862                int save_errno = errno;
2863
2864                strbuf_addf(err, "unable to append to '%s': %s",
2865                            git_path("logs/%s", refname), strerror(save_errno));
2866                return -1;
2867        }
2868        return 0;
2869}
2870
2871/*
2872 * Write sha1 into the open lockfile, then close the lockfile. On
2873 * errors, rollback the lockfile, fill in *err and
2874 * return -1.
2875 */
2876static int write_ref_to_lockfile(struct ref_lock *lock,
2877                                 const unsigned char *sha1, struct strbuf *err)
2878{
2879        static char term = '\n';
2880        struct object *o;
2881        int fd;
2882
2883        o = parse_object(sha1);
2884        if (!o) {
2885                strbuf_addf(err,
2886                            "trying to write ref '%s' with nonexistent object %s",
2887                            lock->ref_name, sha1_to_hex(sha1));
2888                unlock_ref(lock);
2889                return -1;
2890        }
2891        if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
2892                strbuf_addf(err,
2893                            "trying to write non-commit object %s to branch '%s'",
2894                            sha1_to_hex(sha1), lock->ref_name);
2895                unlock_ref(lock);
2896                return -1;
2897        }
2898        fd = get_lock_file_fd(lock->lk);
2899        if (write_in_full(fd, sha1_to_hex(sha1), 40) != 40 ||
2900            write_in_full(fd, &term, 1) != 1 ||
2901            close_ref(lock) < 0) {
2902                strbuf_addf(err,
2903                            "couldn't write '%s'", get_lock_file_path(lock->lk));
2904                unlock_ref(lock);
2905                return -1;
2906        }
2907        return 0;
2908}
2909
2910/*
2911 * Commit a change to a loose reference that has already been written
2912 * to the loose reference lockfile. Also update the reflogs if
2913 * necessary, using the specified lockmsg (which can be NULL).
2914 */
2915static int commit_ref_update(struct files_ref_store *refs,
2916                             struct ref_lock *lock,
2917                             const unsigned char *sha1, const char *logmsg,
2918                             struct strbuf *err)
2919{
2920        files_assert_main_repository(refs, "commit_ref_update");
2921
2922        clear_loose_ref_cache(refs);
2923        if (files_log_ref_write(lock->ref_name, lock->old_oid.hash, sha1,
2924                                logmsg, 0, err)) {
2925                char *old_msg = strbuf_detach(err, NULL);
2926                strbuf_addf(err, "cannot update the ref '%s': %s",
2927                            lock->ref_name, old_msg);
2928                free(old_msg);
2929                unlock_ref(lock);
2930                return -1;
2931        }
2932
2933        if (strcmp(lock->ref_name, "HEAD") != 0) {
2934                /*
2935                 * Special hack: If a branch is updated directly and HEAD
2936                 * points to it (may happen on the remote side of a push
2937                 * for example) then logically the HEAD reflog should be
2938                 * updated too.
2939                 * A generic solution implies reverse symref information,
2940                 * but finding all symrefs pointing to the given branch
2941                 * would be rather costly for this rare event (the direct
2942                 * update of a branch) to be worth it.  So let's cheat and
2943                 * check with HEAD only which should cover 99% of all usage
2944                 * scenarios (even 100% of the default ones).
2945                 */
2946                unsigned char head_sha1[20];
2947                int head_flag;
2948                const char *head_ref;
2949
2950                head_ref = resolve_ref_unsafe("HEAD", RESOLVE_REF_READING,
2951                                              head_sha1, &head_flag);
2952                if (head_ref && (head_flag & REF_ISSYMREF) &&
2953                    !strcmp(head_ref, lock->ref_name)) {
2954                        struct strbuf log_err = STRBUF_INIT;
2955                        if (files_log_ref_write("HEAD", lock->old_oid.hash, sha1,
2956                                          logmsg, 0, &log_err)) {
2957                                error("%s", log_err.buf);
2958                                strbuf_release(&log_err);
2959                        }
2960                }
2961        }
2962
2963        if (commit_ref(lock)) {
2964                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2965                unlock_ref(lock);
2966                return -1;
2967        }
2968
2969        unlock_ref(lock);
2970        return 0;
2971}
2972
2973static int create_ref_symlink(struct ref_lock *lock, const char *target)
2974{
2975        int ret = -1;
2976#ifndef NO_SYMLINK_HEAD
2977        char *ref_path = get_locked_file_path(lock->lk);
2978        unlink(ref_path);
2979        ret = symlink(target, ref_path);
2980        free(ref_path);
2981
2982        if (ret)
2983                fprintf(stderr, "no symlink - falling back to symbolic ref\n");
2984#endif
2985        return ret;
2986}
2987
2988static void update_symref_reflog(struct ref_lock *lock, const char *refname,
2989                                 const char *target, const char *logmsg)
2990{
2991        struct strbuf err = STRBUF_INIT;
2992        unsigned char new_sha1[20];
2993        if (logmsg && !read_ref(target, new_sha1) &&
2994            files_log_ref_write(refname, lock->old_oid.hash, new_sha1,
2995                                logmsg, 0, &err)) {
2996                error("%s", err.buf);
2997                strbuf_release(&err);
2998        }
2999}
3000
3001static int create_symref_locked(struct ref_lock *lock, const char *refname,
3002                                const char *target, const char *logmsg)
3003{
3004        if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
3005                update_symref_reflog(lock, refname, target, logmsg);
3006                return 0;
3007        }
3008
3009        if (!fdopen_lock_file(lock->lk, "w"))
3010                return error("unable to fdopen %s: %s",
3011                             lock->lk->tempfile.filename.buf, strerror(errno));
3012
3013        update_symref_reflog(lock, refname, target, logmsg);
3014
3015        /* no error check; commit_ref will check ferror */
3016        fprintf(lock->lk->tempfile.fp, "ref: %s\n", target);
3017        if (commit_ref(lock) < 0)
3018                return error("unable to write symref for %s: %s", refname,
3019                             strerror(errno));
3020        return 0;
3021}
3022
3023static int files_create_symref(struct ref_store *ref_store,
3024                               const char *refname, const char *target,
3025                               const char *logmsg)
3026{
3027        struct files_ref_store *refs =
3028                files_downcast(ref_store, 0, "create_symref");
3029        struct strbuf err = STRBUF_INIT;
3030        struct ref_lock *lock;
3031        int ret;
3032
3033        lock = lock_ref_sha1_basic(refs, refname, NULL,
3034                                   NULL, NULL, REF_NODEREF, NULL,
3035                                   &err);
3036        if (!lock) {
3037                error("%s", err.buf);
3038                strbuf_release(&err);
3039                return -1;
3040        }
3041
3042        ret = create_symref_locked(lock, refname, target, logmsg);
3043        unlock_ref(lock);
3044        return ret;
3045}
3046
3047int set_worktree_head_symref(const char *gitdir, const char *target, const char *logmsg)
3048{
3049        static struct lock_file head_lock;
3050        struct ref_lock *lock;
3051        struct strbuf head_path = STRBUF_INIT;
3052        const char *head_rel;
3053        int ret;
3054
3055        strbuf_addf(&head_path, "%s/HEAD", absolute_path(gitdir));
3056        if (hold_lock_file_for_update(&head_lock, head_path.buf,
3057                                      LOCK_NO_DEREF) < 0) {
3058                struct strbuf err = STRBUF_INIT;
3059                unable_to_lock_message(head_path.buf, errno, &err);
3060                error("%s", err.buf);
3061                strbuf_release(&err);
3062                strbuf_release(&head_path);
3063                return -1;
3064        }
3065
3066        /* head_rel will be "HEAD" for the main tree, "worktrees/wt/HEAD" for
3067           linked trees */
3068        head_rel = remove_leading_path(head_path.buf,
3069                                       absolute_path(get_git_common_dir()));
3070        /* to make use of create_symref_locked(), initialize ref_lock */
3071        lock = xcalloc(1, sizeof(struct ref_lock));
3072        lock->lk = &head_lock;
3073        lock->ref_name = xstrdup(head_rel);
3074
3075        ret = create_symref_locked(lock, head_rel, target, logmsg);
3076
3077        unlock_ref(lock); /* will free lock */
3078        strbuf_release(&head_path);
3079        return ret;
3080}
3081
3082static int files_reflog_exists(struct ref_store *ref_store,
3083                               const char *refname)
3084{
3085        struct stat st;
3086
3087        /* Check validity (but we don't need the result): */
3088        files_downcast(ref_store, 0, "reflog_exists");
3089
3090        return !lstat(git_path("logs/%s", refname), &st) &&
3091                S_ISREG(st.st_mode);
3092}
3093
3094static int files_delete_reflog(struct ref_store *ref_store,
3095                               const char *refname)
3096{
3097        /* Check validity (but we don't need the result): */
3098        files_downcast(ref_store, 0, "delete_reflog");
3099
3100        return remove_path(git_path("logs/%s", refname));
3101}
3102
3103static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
3104{
3105        unsigned char osha1[20], nsha1[20];
3106        char *email_end, *message;
3107        unsigned long timestamp;
3108        int tz;
3109
3110        /* old SP new SP name <email> SP time TAB msg LF */
3111        if (sb->len < 83 || sb->buf[sb->len - 1] != '\n' ||
3112            get_sha1_hex(sb->buf, osha1) || sb->buf[40] != ' ' ||
3113            get_sha1_hex(sb->buf + 41, nsha1) || sb->buf[81] != ' ' ||
3114            !(email_end = strchr(sb->buf + 82, '>')) ||
3115            email_end[1] != ' ' ||
3116            !(timestamp = strtoul(email_end + 2, &message, 10)) ||
3117            !message || message[0] != ' ' ||
3118            (message[1] != '+' && message[1] != '-') ||
3119            !isdigit(message[2]) || !isdigit(message[3]) ||
3120            !isdigit(message[4]) || !isdigit(message[5]))
3121                return 0; /* corrupt? */
3122        email_end[1] = '\0';
3123        tz = strtol(message + 1, NULL, 10);
3124        if (message[6] != '\t')
3125                message += 6;
3126        else
3127                message += 7;
3128        return fn(osha1, nsha1, sb->buf + 82, timestamp, tz, message, cb_data);
3129}
3130
3131static char *find_beginning_of_line(char *bob, char *scan)
3132{
3133        while (bob < scan && *(--scan) != '\n')
3134                ; /* keep scanning backwards */
3135        /*
3136         * Return either beginning of the buffer, or LF at the end of
3137         * the previous line.
3138         */
3139        return scan;
3140}
3141
3142static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
3143                                             const char *refname,
3144                                             each_reflog_ent_fn fn,
3145                                             void *cb_data)
3146{
3147        struct strbuf sb = STRBUF_INIT;
3148        FILE *logfp;
3149        long pos;
3150        int ret = 0, at_tail = 1;
3151
3152        /* Check validity (but we don't need the result): */
3153        files_downcast(ref_store, 0, "for_each_reflog_ent_reverse");
3154
3155        logfp = fopen(git_path("logs/%s", refname), "r");
3156        if (!logfp)
3157                return -1;
3158
3159        /* Jump to the end */
3160        if (fseek(logfp, 0, SEEK_END) < 0)
3161                return error("cannot seek back reflog for %s: %s",
3162                             refname, strerror(errno));
3163        pos = ftell(logfp);
3164        while (!ret && 0 < pos) {
3165                int cnt;
3166                size_t nread;
3167                char buf[BUFSIZ];
3168                char *endp, *scanp;
3169
3170                /* Fill next block from the end */
3171                cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
3172                if (fseek(logfp, pos - cnt, SEEK_SET))
3173                        return error("cannot seek back reflog for %s: %s",
3174                                     refname, strerror(errno));
3175                nread = fread(buf, cnt, 1, logfp);
3176                if (nread != 1)
3177                        return error("cannot read %d bytes from reflog for %s: %s",
3178                                     cnt, refname, strerror(errno));
3179                pos -= cnt;
3180
3181                scanp = endp = buf + cnt;
3182                if (at_tail && scanp[-1] == '\n')
3183                        /* Looking at the final LF at the end of the file */
3184                        scanp--;
3185                at_tail = 0;
3186
3187                while (buf < scanp) {
3188                        /*
3189                         * terminating LF of the previous line, or the beginning
3190                         * of the buffer.
3191                         */
3192                        char *bp;
3193
3194                        bp = find_beginning_of_line(buf, scanp);
3195
3196                        if (*bp == '\n') {
3197                                /*
3198                                 * The newline is the end of the previous line,
3199                                 * so we know we have complete line starting
3200                                 * at (bp + 1). Prefix it onto any prior data
3201                                 * we collected for the line and process it.
3202                                 */
3203                                strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
3204                                scanp = bp;
3205                                endp = bp + 1;
3206                                ret = show_one_reflog_ent(&sb, fn, cb_data);
3207                                strbuf_reset(&sb);
3208                                if (ret)
3209                                        break;
3210                        } else if (!pos) {
3211                                /*
3212                                 * We are at the start of the buffer, and the
3213                                 * start of the file; there is no previous
3214                                 * line, and we have everything for this one.
3215                                 * Process it, and we can end the loop.
3216                                 */
3217                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
3218                                ret = show_one_reflog_ent(&sb, fn, cb_data);
3219                                strbuf_reset(&sb);
3220                                break;
3221                        }
3222
3223                        if (bp == buf) {
3224                                /*
3225                                 * We are at the start of the buffer, and there
3226                                 * is more file to read backwards. Which means
3227                                 * we are in the middle of a line. Note that we
3228                                 * may get here even if *bp was a newline; that
3229                                 * just means we are at the exact end of the
3230                                 * previous line, rather than some spot in the
3231                                 * middle.
3232                                 *
3233                                 * Save away what we have to be combined with
3234                                 * the data from the next read.
3235                                 */
3236                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
3237                                break;
3238                        }
3239                }
3240
3241        }
3242        if (!ret && sb.len)
3243                die("BUG: reverse reflog parser had leftover data");
3244
3245        fclose(logfp);
3246        strbuf_release(&sb);
3247        return ret;
3248}
3249
3250static int files_for_each_reflog_ent(struct ref_store *ref_store,
3251                                     const char *refname,
3252                                     each_reflog_ent_fn fn, void *cb_data)
3253{
3254        FILE *logfp;
3255        struct strbuf sb = STRBUF_INIT;
3256        int ret = 0;
3257
3258        /* Check validity (but we don't need the result): */
3259        files_downcast(ref_store, 0, "for_each_reflog_ent");
3260
3261        logfp = fopen(git_path("logs/%s", refname), "r");
3262        if (!logfp)
3263                return -1;
3264
3265        while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
3266                ret = show_one_reflog_ent(&sb, fn, cb_data);
3267        fclose(logfp);
3268        strbuf_release(&sb);
3269        return ret;
3270}
3271
3272struct files_reflog_iterator {
3273        struct ref_iterator base;
3274
3275        struct dir_iterator *dir_iterator;
3276        struct object_id oid;
3277};
3278
3279static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
3280{
3281        struct files_reflog_iterator *iter =
3282                (struct files_reflog_iterator *)ref_iterator;
3283        struct dir_iterator *diter = iter->dir_iterator;
3284        int ok;
3285
3286        while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
3287                int flags;
3288
3289                if (!S_ISREG(diter->st.st_mode))
3290                        continue;
3291                if (diter->basename[0] == '.')
3292                        continue;
3293                if (ends_with(diter->basename, ".lock"))
3294                        continue;
3295
3296                if (read_ref_full(diter->relative_path, 0,
3297                                  iter->oid.hash, &flags)) {
3298                        error("bad ref for %s", diter->path.buf);
3299                        continue;
3300                }
3301
3302                iter->base.refname = diter->relative_path;
3303                iter->base.oid = &iter->oid;
3304                iter->base.flags = flags;
3305                return ITER_OK;
3306        }
3307
3308        iter->dir_iterator = NULL;
3309        if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
3310                ok = ITER_ERROR;
3311        return ok;
3312}
3313
3314static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
3315                                   struct object_id *peeled)
3316{
3317        die("BUG: ref_iterator_peel() called for reflog_iterator");
3318}
3319
3320static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
3321{
3322        struct files_reflog_iterator *iter =
3323                (struct files_reflog_iterator *)ref_iterator;
3324        int ok = ITER_DONE;
3325
3326        if (iter->dir_iterator)
3327                ok = dir_iterator_abort(iter->dir_iterator);
3328
3329        base_ref_iterator_free(ref_iterator);
3330        return ok;
3331}
3332
3333static struct ref_iterator_vtable files_reflog_iterator_vtable = {
3334        files_reflog_iterator_advance,
3335        files_reflog_iterator_peel,
3336        files_reflog_iterator_abort
3337};
3338
3339static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
3340{
3341        struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
3342        struct ref_iterator *ref_iterator = &iter->base;
3343
3344        /* Check validity (but we don't need the result): */
3345        files_downcast(ref_store, 0, "reflog_iterator_begin");
3346
3347        base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
3348        iter->dir_iterator = dir_iterator_begin(git_path("logs"));
3349        return ref_iterator;
3350}
3351
3352static int ref_update_reject_duplicates(struct string_list *refnames,
3353                                        struct strbuf *err)
3354{
3355        int i, n = refnames->nr;
3356
3357        assert(err);
3358
3359        for (i = 1; i < n; i++)
3360                if (!strcmp(refnames->items[i - 1].string, refnames->items[i].string)) {
3361                        strbuf_addf(err,
3362                                    "multiple updates for ref '%s' not allowed.",
3363                                    refnames->items[i].string);
3364                        return 1;
3365                }
3366        return 0;
3367}
3368
3369/*
3370 * If update is a direct update of head_ref (the reference pointed to
3371 * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
3372 */
3373static int split_head_update(struct ref_update *update,
3374                             struct ref_transaction *transaction,
3375                             const char *head_ref,
3376                             struct string_list *affected_refnames,
3377                             struct strbuf *err)
3378{
3379        struct string_list_item *item;
3380        struct ref_update *new_update;
3381
3382        if ((update->flags & REF_LOG_ONLY) ||
3383            (update->flags & REF_ISPRUNING) ||
3384            (update->flags & REF_UPDATE_VIA_HEAD))
3385                return 0;
3386
3387        if (strcmp(update->refname, head_ref))
3388                return 0;
3389
3390        /*
3391         * First make sure that HEAD is not already in the
3392         * transaction. This insertion is O(N) in the transaction
3393         * size, but it happens at most once per transaction.
3394         */
3395        item = string_list_insert(affected_refnames, "HEAD");
3396        if (item->util) {
3397                /* An entry already existed */
3398                strbuf_addf(err,
3399                            "multiple updates for 'HEAD' (including one "
3400                            "via its referent '%s') are not allowed",
3401                            update->refname);
3402                return TRANSACTION_NAME_CONFLICT;
3403        }
3404
3405        new_update = ref_transaction_add_update(
3406                        transaction, "HEAD",
3407                        update->flags | REF_LOG_ONLY | REF_NODEREF,
3408                        update->new_sha1, update->old_sha1,
3409                        update->msg);
3410
3411        item->util = new_update;
3412
3413        return 0;
3414}
3415
3416/*
3417 * update is for a symref that points at referent and doesn't have
3418 * REF_NODEREF set. Split it into two updates:
3419 * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
3420 * - A new, separate update for the referent reference
3421 * Note that the new update will itself be subject to splitting when
3422 * the iteration gets to it.
3423 */
3424static int split_symref_update(struct files_ref_store *refs,
3425                               struct ref_update *update,
3426                               const char *referent,
3427                               struct ref_transaction *transaction,
3428                               struct string_list *affected_refnames,
3429                               struct strbuf *err)
3430{
3431        struct string_list_item *item;
3432        struct ref_update *new_update;
3433        unsigned int new_flags;
3434
3435        /*
3436         * First make sure that referent is not already in the
3437         * transaction. This insertion is O(N) in the transaction
3438         * size, but it happens at most once per symref in a
3439         * transaction.
3440         */
3441        item = string_list_insert(affected_refnames, referent);
3442        if (item->util) {
3443                /* An entry already existed */
3444                strbuf_addf(err,
3445                            "multiple updates for '%s' (including one "
3446                            "via symref '%s') are not allowed",
3447                            referent, update->refname);
3448                return TRANSACTION_NAME_CONFLICT;
3449        }
3450
3451        new_flags = update->flags;
3452        if (!strcmp(update->refname, "HEAD")) {
3453                /*
3454                 * Record that the new update came via HEAD, so that
3455                 * when we process it, split_head_update() doesn't try
3456                 * to add another reflog update for HEAD. Note that
3457                 * this bit will be propagated if the new_update
3458                 * itself needs to be split.
3459                 */
3460                new_flags |= REF_UPDATE_VIA_HEAD;
3461        }
3462
3463        new_update = ref_transaction_add_update(
3464                        transaction, referent, new_flags,
3465                        update->new_sha1, update->old_sha1,
3466                        update->msg);
3467
3468        new_update->parent_update = update;
3469
3470        /*
3471         * Change the symbolic ref update to log only. Also, it
3472         * doesn't need to check its old SHA-1 value, as that will be
3473         * done when new_update is processed.
3474         */
3475        update->flags |= REF_LOG_ONLY | REF_NODEREF;
3476        update->flags &= ~REF_HAVE_OLD;
3477
3478        item->util = new_update;
3479
3480        return 0;
3481}
3482
3483/*
3484 * Return the refname under which update was originally requested.
3485 */
3486static const char *original_update_refname(struct ref_update *update)
3487{
3488        while (update->parent_update)
3489                update = update->parent_update;
3490
3491        return update->refname;
3492}
3493
3494/*
3495 * Check whether the REF_HAVE_OLD and old_oid values stored in update
3496 * are consistent with oid, which is the reference's current value. If
3497 * everything is OK, return 0; otherwise, write an error message to
3498 * err and return -1.
3499 */
3500static int check_old_oid(struct ref_update *update, struct object_id *oid,
3501                         struct strbuf *err)
3502{
3503        if (!(update->flags & REF_HAVE_OLD) ||
3504                   !hashcmp(oid->hash, update->old_sha1))
3505                return 0;
3506
3507        if (is_null_sha1(update->old_sha1))
3508                strbuf_addf(err, "cannot lock ref '%s': "
3509                            "reference already exists",
3510                            original_update_refname(update));
3511        else if (is_null_oid(oid))
3512                strbuf_addf(err, "cannot lock ref '%s': "
3513                            "reference is missing but expected %s",
3514                            original_update_refname(update),
3515                            sha1_to_hex(update->old_sha1));
3516        else
3517                strbuf_addf(err, "cannot lock ref '%s': "
3518                            "is at %s but expected %s",
3519                            original_update_refname(update),
3520                            oid_to_hex(oid),
3521                            sha1_to_hex(update->old_sha1));
3522
3523        return -1;
3524}
3525
3526/*
3527 * Prepare for carrying out update:
3528 * - Lock the reference referred to by update.
3529 * - Read the reference under lock.
3530 * - Check that its old SHA-1 value (if specified) is correct, and in
3531 *   any case record it in update->lock->old_oid for later use when
3532 *   writing the reflog.
3533 * - If it is a symref update without REF_NODEREF, split it up into a
3534 *   REF_LOG_ONLY update of the symref and add a separate update for
3535 *   the referent to transaction.
3536 * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
3537 *   update of HEAD.
3538 */
3539static int lock_ref_for_update(struct files_ref_store *refs,
3540                               struct ref_update *update,
3541                               struct ref_transaction *transaction,
3542                               const char *head_ref,
3543                               struct string_list *affected_refnames,
3544                               struct strbuf *err)
3545{
3546        struct strbuf referent = STRBUF_INIT;
3547        int mustexist = (update->flags & REF_HAVE_OLD) &&
3548                !is_null_sha1(update->old_sha1);
3549        int ret;
3550        struct ref_lock *lock;
3551
3552        files_assert_main_repository(refs, "lock_ref_for_update");
3553
3554        if ((update->flags & REF_HAVE_NEW) && is_null_sha1(update->new_sha1))
3555                update->flags |= REF_DELETING;
3556
3557        if (head_ref) {
3558                ret = split_head_update(update, transaction, head_ref,
3559                                        affected_refnames, err);
3560                if (ret)
3561                        return ret;
3562        }
3563
3564        ret = lock_raw_ref(refs, update->refname, mustexist,
3565                           affected_refnames, NULL,
3566                           &lock, &referent,
3567                           &update->type, err);
3568        if (ret) {
3569                char *reason;
3570
3571                reason = strbuf_detach(err, NULL);
3572                strbuf_addf(err, "cannot lock ref '%s': %s",
3573                            original_update_refname(update), reason);
3574                free(reason);
3575                return ret;
3576        }
3577
3578        update->backend_data = lock;
3579
3580        if (update->type & REF_ISSYMREF) {
3581                if (update->flags & REF_NODEREF) {
3582                        /*
3583                         * We won't be reading the referent as part of
3584                         * the transaction, so we have to read it here
3585                         * to record and possibly check old_sha1:
3586                         */
3587                        if (read_ref_full(referent.buf, 0,
3588                                          lock->old_oid.hash, NULL)) {
3589                                if (update->flags & REF_HAVE_OLD) {
3590                                        strbuf_addf(err, "cannot lock ref '%s': "
3591                                                    "error reading reference",
3592                                                    original_update_refname(update));
3593                                        return -1;
3594                                }
3595                        } else if (check_old_oid(update, &lock->old_oid, err)) {
3596                                return TRANSACTION_GENERIC_ERROR;
3597                        }
3598                } else {
3599                        /*
3600                         * Create a new update for the reference this
3601                         * symref is pointing at. Also, we will record
3602                         * and verify old_sha1 for this update as part
3603                         * of processing the split-off update, so we
3604                         * don't have to do it here.
3605                         */
3606                        ret = split_symref_update(refs, update,
3607                                                  referent.buf, transaction,
3608                                                  affected_refnames, err);
3609                        if (ret)
3610                                return ret;
3611                }
3612        } else {
3613                struct ref_update *parent_update;
3614
3615                if (check_old_oid(update, &lock->old_oid, err))
3616                        return TRANSACTION_GENERIC_ERROR;
3617
3618                /*
3619                 * If this update is happening indirectly because of a
3620                 * symref update, record the old SHA-1 in the parent
3621                 * update:
3622                 */
3623                for (parent_update = update->parent_update;
3624                     parent_update;
3625                     parent_update = parent_update->parent_update) {
3626                        struct ref_lock *parent_lock = parent_update->backend_data;
3627                        oidcpy(&parent_lock->old_oid, &lock->old_oid);
3628                }
3629        }
3630
3631        if ((update->flags & REF_HAVE_NEW) &&
3632            !(update->flags & REF_DELETING) &&
3633            !(update->flags & REF_LOG_ONLY)) {
3634                if (!(update->type & REF_ISSYMREF) &&
3635                    !hashcmp(lock->old_oid.hash, update->new_sha1)) {
3636                        /*
3637                         * The reference already has the desired
3638                         * value, so we don't need to write it.
3639                         */
3640                } else if (write_ref_to_lockfile(lock, update->new_sha1,
3641                                                 err)) {
3642                        char *write_err = strbuf_detach(err, NULL);
3643
3644                        /*
3645                         * The lock was freed upon failure of
3646                         * write_ref_to_lockfile():
3647                         */
3648                        update->backend_data = NULL;
3649                        strbuf_addf(err,
3650                                    "cannot update ref '%s': %s",
3651                                    update->refname, write_err);
3652                        free(write_err);
3653                        return TRANSACTION_GENERIC_ERROR;
3654                } else {
3655                        update->flags |= REF_NEEDS_COMMIT;
3656                }
3657        }
3658        if (!(update->flags & REF_NEEDS_COMMIT)) {
3659                /*
3660                 * We didn't call write_ref_to_lockfile(), so
3661                 * the lockfile is still open. Close it to
3662                 * free up the file descriptor:
3663                 */
3664                if (close_ref(lock)) {
3665                        strbuf_addf(err, "couldn't close '%s.lock'",
3666                                    update->refname);
3667                        return TRANSACTION_GENERIC_ERROR;
3668                }
3669        }
3670        return 0;
3671}
3672
3673static int files_transaction_commit(struct ref_store *ref_store,
3674                                    struct ref_transaction *transaction,
3675                                    struct strbuf *err)
3676{
3677        struct files_ref_store *refs =
3678                files_downcast(ref_store, 0, "ref_transaction_commit");
3679        int ret = 0, i;
3680        struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
3681        struct string_list_item *ref_to_delete;
3682        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
3683        char *head_ref = NULL;
3684        int head_type;
3685        struct object_id head_oid;
3686
3687        assert(err);
3688
3689        if (transaction->state != REF_TRANSACTION_OPEN)
3690                die("BUG: commit called for transaction that is not open");
3691
3692        if (!transaction->nr) {
3693                transaction->state = REF_TRANSACTION_CLOSED;
3694                return 0;
3695        }
3696
3697        /*
3698         * Fail if a refname appears more than once in the
3699         * transaction. (If we end up splitting up any updates using
3700         * split_symref_update() or split_head_update(), those
3701         * functions will check that the new updates don't have the
3702         * same refname as any existing ones.)
3703         */
3704        for (i = 0; i < transaction->nr; i++) {
3705                struct ref_update *update = transaction->updates[i];
3706                struct string_list_item *item =
3707                        string_list_append(&affected_refnames, update->refname);
3708
3709                /*
3710                 * We store a pointer to update in item->util, but at
3711                 * the moment we never use the value of this field
3712                 * except to check whether it is non-NULL.
3713                 */
3714                item->util = update;
3715        }
3716        string_list_sort(&affected_refnames);
3717        if (ref_update_reject_duplicates(&affected_refnames, err)) {
3718                ret = TRANSACTION_GENERIC_ERROR;
3719                goto cleanup;
3720        }
3721
3722        /*
3723         * Special hack: If a branch is updated directly and HEAD
3724         * points to it (may happen on the remote side of a push
3725         * for example) then logically the HEAD reflog should be
3726         * updated too.
3727         *
3728         * A generic solution would require reverse symref lookups,
3729         * but finding all symrefs pointing to a given branch would be
3730         * rather costly for this rare event (the direct update of a
3731         * branch) to be worth it. So let's cheat and check with HEAD
3732         * only, which should cover 99% of all usage scenarios (even
3733         * 100% of the default ones).
3734         *
3735         * So if HEAD is a symbolic reference, then record the name of
3736         * the reference that it points to. If we see an update of
3737         * head_ref within the transaction, then split_head_update()
3738         * arranges for the reflog of HEAD to be updated, too.
3739         */
3740        head_ref = resolve_refdup("HEAD", RESOLVE_REF_NO_RECURSE,
3741                                  head_oid.hash, &head_type);
3742
3743        if (head_ref && !(head_type & REF_ISSYMREF)) {
3744                free(head_ref);
3745                head_ref = NULL;
3746        }
3747
3748        /*
3749         * Acquire all locks, verify old values if provided, check
3750         * that new values are valid, and write new values to the
3751         * lockfiles, ready to be activated. Only keep one lockfile
3752         * open at a time to avoid running out of file descriptors.
3753         */
3754        for (i = 0; i < transaction->nr; i++) {
3755                struct ref_update *update = transaction->updates[i];
3756
3757                ret = lock_ref_for_update(refs, update, transaction,
3758                                          head_ref, &affected_refnames, err);
3759                if (ret)
3760                        goto cleanup;
3761        }
3762
3763        /* Perform updates first so live commits remain referenced */
3764        for (i = 0; i < transaction->nr; i++) {
3765                struct ref_update *update = transaction->updates[i];
3766                struct ref_lock *lock = update->backend_data;
3767
3768                if (update->flags & REF_NEEDS_COMMIT ||
3769                    update->flags & REF_LOG_ONLY) {
3770                        if (files_log_ref_write(lock->ref_name,
3771                                                lock->old_oid.hash,
3772                                                update->new_sha1,
3773                                                update->msg, update->flags,
3774                                                err)) {
3775                                char *old_msg = strbuf_detach(err, NULL);
3776
3777                                strbuf_addf(err, "cannot update the ref '%s': %s",
3778                                            lock->ref_name, old_msg);
3779                                free(old_msg);
3780                                unlock_ref(lock);
3781                                update->backend_data = NULL;
3782                                ret = TRANSACTION_GENERIC_ERROR;
3783                                goto cleanup;
3784                        }
3785                }
3786                if (update->flags & REF_NEEDS_COMMIT) {
3787                        clear_loose_ref_cache(refs);
3788                        if (commit_ref(lock)) {
3789                                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
3790                                unlock_ref(lock);
3791                                update->backend_data = NULL;
3792                                ret = TRANSACTION_GENERIC_ERROR;
3793                                goto cleanup;
3794                        }
3795                }
3796        }
3797        /* Perform deletes now that updates are safely completed */
3798        for (i = 0; i < transaction->nr; i++) {
3799                struct ref_update *update = transaction->updates[i];
3800                struct ref_lock *lock = update->backend_data;
3801
3802                if (update->flags & REF_DELETING &&
3803                    !(update->flags & REF_LOG_ONLY)) {
3804                        if (!(update->type & REF_ISPACKED) ||
3805                            update->type & REF_ISSYMREF) {
3806                                /* It is a loose reference. */
3807                                if (unlink_or_msg(git_path("%s", lock->ref_name), err)) {
3808                                        ret = TRANSACTION_GENERIC_ERROR;
3809                                        goto cleanup;
3810                                }
3811                                update->flags |= REF_DELETED_LOOSE;
3812                        }
3813
3814                        if (!(update->flags & REF_ISPRUNING))
3815                                string_list_append(&refs_to_delete,
3816                                                   lock->ref_name);
3817                }
3818        }
3819
3820        if (repack_without_refs(refs, &refs_to_delete, err)) {
3821                ret = TRANSACTION_GENERIC_ERROR;
3822                goto cleanup;
3823        }
3824
3825        /* Delete the reflogs of any references that were deleted: */
3826        for_each_string_list_item(ref_to_delete, &refs_to_delete) {
3827                if (!unlink_or_warn(git_path("logs/%s", ref_to_delete->string)))
3828                        try_remove_empty_parents(ref_to_delete->string,
3829                                                 REMOVE_EMPTY_PARENTS_REFLOG);
3830        }
3831
3832        clear_loose_ref_cache(refs);
3833
3834cleanup:
3835        transaction->state = REF_TRANSACTION_CLOSED;
3836
3837        for (i = 0; i < transaction->nr; i++) {
3838                struct ref_update *update = transaction->updates[i];
3839                struct ref_lock *lock = update->backend_data;
3840
3841                if (lock)
3842                        unlock_ref(lock);
3843
3844                if (update->flags & REF_DELETED_LOOSE) {
3845                        /*
3846                         * The loose reference was deleted. Delete any
3847                         * empty parent directories. (Note that this
3848                         * can only work because we have already
3849                         * removed the lockfile.)
3850                         */
3851                        try_remove_empty_parents(update->refname,
3852                                                 REMOVE_EMPTY_PARENTS_REF);
3853                }
3854        }
3855
3856        string_list_clear(&refs_to_delete, 0);
3857        free(head_ref);
3858        string_list_clear(&affected_refnames, 0);
3859
3860        return ret;
3861}
3862
3863static int ref_present(const char *refname,
3864                       const struct object_id *oid, int flags, void *cb_data)
3865{
3866        struct string_list *affected_refnames = cb_data;
3867
3868        return string_list_has_string(affected_refnames, refname);
3869}
3870
3871static int files_initial_transaction_commit(struct ref_store *ref_store,
3872                                            struct ref_transaction *transaction,
3873                                            struct strbuf *err)
3874{
3875        struct files_ref_store *refs =
3876                files_downcast(ref_store, 0, "initial_ref_transaction_commit");
3877        int ret = 0, i;
3878        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
3879
3880        assert(err);
3881
3882        if (transaction->state != REF_TRANSACTION_OPEN)
3883                die("BUG: commit called for transaction that is not open");
3884
3885        /* Fail if a refname appears more than once in the transaction: */
3886        for (i = 0; i < transaction->nr; i++)
3887                string_list_append(&affected_refnames,
3888                                   transaction->updates[i]->refname);
3889        string_list_sort(&affected_refnames);
3890        if (ref_update_reject_duplicates(&affected_refnames, err)) {
3891                ret = TRANSACTION_GENERIC_ERROR;
3892                goto cleanup;
3893        }
3894
3895        /*
3896         * It's really undefined to call this function in an active
3897         * repository or when there are existing references: we are
3898         * only locking and changing packed-refs, so (1) any
3899         * simultaneous processes might try to change a reference at
3900         * the same time we do, and (2) any existing loose versions of
3901         * the references that we are setting would have precedence
3902         * over our values. But some remote helpers create the remote
3903         * "HEAD" and "master" branches before calling this function,
3904         * so here we really only check that none of the references
3905         * that we are creating already exists.
3906         */
3907        if (for_each_rawref(ref_present, &affected_refnames))
3908                die("BUG: initial ref transaction called with existing refs");
3909
3910        for (i = 0; i < transaction->nr; i++) {
3911                struct ref_update *update = transaction->updates[i];
3912
3913                if ((update->flags & REF_HAVE_OLD) &&
3914                    !is_null_sha1(update->old_sha1))
3915                        die("BUG: initial ref transaction with old_sha1 set");
3916                if (verify_refname_available(update->refname,
3917                                             &affected_refnames, NULL,
3918                                             err)) {
3919                        ret = TRANSACTION_NAME_CONFLICT;
3920                        goto cleanup;
3921                }
3922        }
3923
3924        if (lock_packed_refs(refs, 0)) {
3925                strbuf_addf(err, "unable to lock packed-refs file: %s",
3926                            strerror(errno));
3927                ret = TRANSACTION_GENERIC_ERROR;
3928                goto cleanup;
3929        }
3930
3931        for (i = 0; i < transaction->nr; i++) {
3932                struct ref_update *update = transaction->updates[i];
3933
3934                if ((update->flags & REF_HAVE_NEW) &&
3935                    !is_null_sha1(update->new_sha1))
3936                        add_packed_ref(refs, update->refname, update->new_sha1);
3937        }
3938
3939        if (commit_packed_refs(refs)) {
3940                strbuf_addf(err, "unable to commit packed-refs file: %s",
3941                            strerror(errno));
3942                ret = TRANSACTION_GENERIC_ERROR;
3943                goto cleanup;
3944        }
3945
3946cleanup:
3947        transaction->state = REF_TRANSACTION_CLOSED;
3948        string_list_clear(&affected_refnames, 0);
3949        return ret;
3950}
3951
3952struct expire_reflog_cb {
3953        unsigned int flags;
3954        reflog_expiry_should_prune_fn *should_prune_fn;
3955        void *policy_cb;
3956        FILE *newlog;
3957        unsigned char last_kept_sha1[20];
3958};
3959
3960static int expire_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
3961                             const char *email, unsigned long timestamp, int tz,
3962                             const char *message, void *cb_data)
3963{
3964        struct expire_reflog_cb *cb = cb_data;
3965        struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
3966
3967        if (cb->flags & EXPIRE_REFLOGS_REWRITE)
3968                osha1 = cb->last_kept_sha1;
3969
3970        if ((*cb->should_prune_fn)(osha1, nsha1, email, timestamp, tz,
3971                                   message, policy_cb)) {
3972                if (!cb->newlog)
3973                        printf("would prune %s", message);
3974                else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3975                        printf("prune %s", message);
3976        } else {
3977                if (cb->newlog) {
3978                        fprintf(cb->newlog, "%s %s %s %lu %+05d\t%s",
3979                                sha1_to_hex(osha1), sha1_to_hex(nsha1),
3980                                email, timestamp, tz, message);
3981                        hashcpy(cb->last_kept_sha1, nsha1);
3982                }
3983                if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3984                        printf("keep %s", message);
3985        }
3986        return 0;
3987}
3988
3989static int files_reflog_expire(struct ref_store *ref_store,
3990                               const char *refname, const unsigned char *sha1,
3991                               unsigned int flags,
3992                               reflog_expiry_prepare_fn prepare_fn,
3993                               reflog_expiry_should_prune_fn should_prune_fn,
3994                               reflog_expiry_cleanup_fn cleanup_fn,
3995                               void *policy_cb_data)
3996{
3997        struct files_ref_store *refs =
3998                files_downcast(ref_store, 0, "reflog_expire");
3999        static struct lock_file reflog_lock;
4000        struct expire_reflog_cb cb;
4001        struct ref_lock *lock;
4002        char *log_file;
4003        int status = 0;
4004        int type;
4005        struct strbuf err = STRBUF_INIT;
4006
4007        memset(&cb, 0, sizeof(cb));
4008        cb.flags = flags;
4009        cb.policy_cb = policy_cb_data;
4010        cb.should_prune_fn = should_prune_fn;
4011
4012        /*
4013         * The reflog file is locked by holding the lock on the
4014         * reference itself, plus we might need to update the
4015         * reference if --updateref was specified:
4016         */
4017        lock = lock_ref_sha1_basic(refs, refname, sha1,
4018                                   NULL, NULL, REF_NODEREF,
4019                                   &type, &err);
4020        if (!lock) {
4021                error("cannot lock ref '%s': %s", refname, err.buf);
4022                strbuf_release(&err);
4023                return -1;
4024        }
4025        if (!reflog_exists(refname)) {
4026                unlock_ref(lock);
4027                return 0;
4028        }
4029
4030        log_file = git_pathdup("logs/%s", refname);
4031        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
4032                /*
4033                 * Even though holding $GIT_DIR/logs/$reflog.lock has
4034                 * no locking implications, we use the lock_file
4035                 * machinery here anyway because it does a lot of the
4036                 * work we need, including cleaning up if the program
4037                 * exits unexpectedly.
4038                 */
4039                if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
4040                        struct strbuf err = STRBUF_INIT;
4041                        unable_to_lock_message(log_file, errno, &err);
4042                        error("%s", err.buf);
4043                        strbuf_release(&err);
4044                        goto failure;
4045                }
4046                cb.newlog = fdopen_lock_file(&reflog_lock, "w");
4047                if (!cb.newlog) {
4048                        error("cannot fdopen %s (%s)",
4049                              get_lock_file_path(&reflog_lock), strerror(errno));
4050                        goto failure;
4051                }
4052        }
4053
4054        (*prepare_fn)(refname, sha1, cb.policy_cb);
4055        for_each_reflog_ent(refname, expire_reflog_ent, &cb);
4056        (*cleanup_fn)(cb.policy_cb);
4057
4058        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
4059                /*
4060                 * It doesn't make sense to adjust a reference pointed
4061                 * to by a symbolic ref based on expiring entries in
4062                 * the symbolic reference's reflog. Nor can we update
4063                 * a reference if there are no remaining reflog
4064                 * entries.
4065                 */
4066                int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
4067                        !(type & REF_ISSYMREF) &&
4068                        !is_null_sha1(cb.last_kept_sha1);
4069
4070                if (close_lock_file(&reflog_lock)) {
4071                        status |= error("couldn't write %s: %s", log_file,
4072                                        strerror(errno));
4073                } else if (update &&
4074                           (write_in_full(get_lock_file_fd(lock->lk),
4075                                sha1_to_hex(cb.last_kept_sha1), 40) != 40 ||
4076                            write_str_in_full(get_lock_file_fd(lock->lk), "\n") != 1 ||
4077                            close_ref(lock) < 0)) {
4078                        status |= error("couldn't write %s",
4079                                        get_lock_file_path(lock->lk));
4080                        rollback_lock_file(&reflog_lock);
4081                } else if (commit_lock_file(&reflog_lock)) {
4082                        status |= error("unable to write reflog '%s' (%s)",
4083                                        log_file, strerror(errno));
4084                } else if (update && commit_ref(lock)) {
4085                        status |= error("couldn't set %s", lock->ref_name);
4086                }
4087        }
4088        free(log_file);
4089        unlock_ref(lock);
4090        return status;
4091
4092 failure:
4093        rollback_lock_file(&reflog_lock);
4094        free(log_file);
4095        unlock_ref(lock);
4096        return -1;
4097}
4098
4099static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
4100{
4101        /* Check validity (but we don't need the result): */
4102        files_downcast(ref_store, 0, "init_db");
4103
4104        /*
4105         * Create .git/refs/{heads,tags}
4106         */
4107        safe_create_dir(git_path("refs/heads"), 1);
4108        safe_create_dir(git_path("refs/tags"), 1);
4109        if (get_shared_repository()) {
4110                adjust_shared_perm(git_path("refs/heads"));
4111                adjust_shared_perm(git_path("refs/tags"));
4112        }
4113        return 0;
4114}
4115
4116struct ref_storage_be refs_be_files = {
4117        NULL,
4118        "files",
4119        files_ref_store_create,
4120        files_init_db,
4121        files_transaction_commit,
4122        files_initial_transaction_commit,
4123
4124        files_pack_refs,
4125        files_peel_ref,
4126        files_create_symref,
4127        files_delete_refs,
4128        files_rename_ref,
4129
4130        files_ref_iterator_begin,
4131        files_read_raw_ref,
4132        files_verify_refname_available,
4133
4134        files_reflog_iterator_begin,
4135        files_for_each_reflog_ent,
4136        files_for_each_reflog_ent_reverse,
4137        files_reflog_exists,
4138        files_create_reflog,
4139        files_delete_reflog,
4140        files_reflog_expire
4141};