refs / files-backend.con commit Merge branch 'lt/pathspec-negative' (015fba3)
   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        struct ref_entry *loose;
 916        struct packed_ref_cache *packed;
 917};
 918
 919/* Lock used for the main packed-refs file: */
 920static struct lock_file packlock;
 921
 922/*
 923 * Increment the reference count of *packed_refs.
 924 */
 925static void acquire_packed_ref_cache(struct packed_ref_cache *packed_refs)
 926{
 927        packed_refs->referrers++;
 928}
 929
 930/*
 931 * Decrease the reference count of *packed_refs.  If it goes to zero,
 932 * free *packed_refs and return true; otherwise return false.
 933 */
 934static int release_packed_ref_cache(struct packed_ref_cache *packed_refs)
 935{
 936        if (!--packed_refs->referrers) {
 937                free_ref_entry(packed_refs->root);
 938                stat_validity_clear(&packed_refs->validity);
 939                free(packed_refs);
 940                return 1;
 941        } else {
 942                return 0;
 943        }
 944}
 945
 946static void clear_packed_ref_cache(struct files_ref_store *refs)
 947{
 948        if (refs->packed) {
 949                struct packed_ref_cache *packed_refs = refs->packed;
 950
 951                if (packed_refs->lock)
 952                        die("internal error: packed-ref cache cleared while locked");
 953                refs->packed = NULL;
 954                release_packed_ref_cache(packed_refs);
 955        }
 956}
 957
 958static void clear_loose_ref_cache(struct files_ref_store *refs)
 959{
 960        if (refs->loose) {
 961                free_ref_entry(refs->loose);
 962                refs->loose = NULL;
 963        }
 964}
 965
 966/*
 967 * Create a new submodule ref cache and add it to the internal
 968 * set of caches.
 969 */
 970static struct ref_store *files_ref_store_create(const char *submodule)
 971{
 972        struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
 973        struct ref_store *ref_store = (struct ref_store *)refs;
 974
 975        base_ref_store_init(ref_store, &refs_be_files, submodule);
 976
 977        return ref_store;
 978}
 979
 980/*
 981 * Downcast ref_store to files_ref_store. Die if ref_store is not a
 982 * files_ref_store. If submodule_allowed is not true, then also die if
 983 * files_ref_store is for a submodule (i.e., not for the main
 984 * repository). caller is used in any necessary error messages.
 985 */
 986static struct files_ref_store *files_downcast(
 987                struct ref_store *ref_store, int submodule_allowed,
 988                const char *caller)
 989{
 990        if (ref_store->be != &refs_be_files)
 991                die("BUG: ref_store is type \"%s\" not \"files\" in %s",
 992                    ref_store->be->name, caller);
 993
 994        if (!submodule_allowed)
 995                assert_main_repository(ref_store, caller);
 996
 997        return (struct files_ref_store *)ref_store;
 998}
 999
1000/* The length of a peeled reference line in packed-refs, including EOL: */
1001#define PEELED_LINE_LENGTH 42
1002
1003/*
1004 * The packed-refs header line that we write out.  Perhaps other
1005 * traits will be added later.  The trailing space is required.
1006 */
1007static const char PACKED_REFS_HEADER[] =
1008        "# pack-refs with: peeled fully-peeled \n";
1009
1010/*
1011 * Parse one line from a packed-refs file.  Write the SHA1 to sha1.
1012 * Return a pointer to the refname within the line (null-terminated),
1013 * or NULL if there was a problem.
1014 */
1015static const char *parse_ref_line(struct strbuf *line, unsigned char *sha1)
1016{
1017        const char *ref;
1018
1019        /*
1020         * 42: the answer to everything.
1021         *
1022         * In this case, it happens to be the answer to
1023         *  40 (length of sha1 hex representation)
1024         *  +1 (space in between hex and name)
1025         *  +1 (newline at the end of the line)
1026         */
1027        if (line->len <= 42)
1028                return NULL;
1029
1030        if (get_sha1_hex(line->buf, sha1) < 0)
1031                return NULL;
1032        if (!isspace(line->buf[40]))
1033                return NULL;
1034
1035        ref = line->buf + 41;
1036        if (isspace(*ref))
1037                return NULL;
1038
1039        if (line->buf[line->len - 1] != '\n')
1040                return NULL;
1041        line->buf[--line->len] = 0;
1042
1043        return ref;
1044}
1045
1046/*
1047 * Read f, which is a packed-refs file, into dir.
1048 *
1049 * A comment line of the form "# pack-refs with: " may contain zero or
1050 * more traits. We interpret the traits as follows:
1051 *
1052 *   No traits:
1053 *
1054 *      Probably no references are peeled. But if the file contains a
1055 *      peeled value for a reference, we will use it.
1056 *
1057 *   peeled:
1058 *
1059 *      References under "refs/tags/", if they *can* be peeled, *are*
1060 *      peeled in this file. References outside of "refs/tags/" are
1061 *      probably not peeled even if they could have been, but if we find
1062 *      a peeled value for such a reference we will use it.
1063 *
1064 *   fully-peeled:
1065 *
1066 *      All references in the file that can be peeled are peeled.
1067 *      Inversely (and this is more important), any references in the
1068 *      file for which no peeled value is recorded is not peelable. This
1069 *      trait should typically be written alongside "peeled" for
1070 *      compatibility with older clients, but we do not require it
1071 *      (i.e., "peeled" is a no-op if "fully-peeled" is set).
1072 */
1073static void read_packed_refs(FILE *f, struct ref_dir *dir)
1074{
1075        struct ref_entry *last = NULL;
1076        struct strbuf line = STRBUF_INIT;
1077        enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled = PEELED_NONE;
1078
1079        while (strbuf_getwholeline(&line, f, '\n') != EOF) {
1080                unsigned char sha1[20];
1081                const char *refname;
1082                const char *traits;
1083
1084                if (skip_prefix(line.buf, "# pack-refs with:", &traits)) {
1085                        if (strstr(traits, " fully-peeled "))
1086                                peeled = PEELED_FULLY;
1087                        else if (strstr(traits, " peeled "))
1088                                peeled = PEELED_TAGS;
1089                        /* perhaps other traits later as well */
1090                        continue;
1091                }
1092
1093                refname = parse_ref_line(&line, sha1);
1094                if (refname) {
1095                        int flag = REF_ISPACKED;
1096
1097                        if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
1098                                if (!refname_is_safe(refname))
1099                                        die("packed refname is dangerous: %s", refname);
1100                                hashclr(sha1);
1101                                flag |= REF_BAD_NAME | REF_ISBROKEN;
1102                        }
1103                        last = create_ref_entry(refname, sha1, flag, 0);
1104                        if (peeled == PEELED_FULLY ||
1105                            (peeled == PEELED_TAGS && starts_with(refname, "refs/tags/")))
1106                                last->flag |= REF_KNOWS_PEELED;
1107                        add_ref(dir, last);
1108                        continue;
1109                }
1110                if (last &&
1111                    line.buf[0] == '^' &&
1112                    line.len == PEELED_LINE_LENGTH &&
1113                    line.buf[PEELED_LINE_LENGTH - 1] == '\n' &&
1114                    !get_sha1_hex(line.buf + 1, sha1)) {
1115                        hashcpy(last->u.value.peeled.hash, sha1);
1116                        /*
1117                         * Regardless of what the file header said,
1118                         * we definitely know the value of *this*
1119                         * reference:
1120                         */
1121                        last->flag |= REF_KNOWS_PEELED;
1122                }
1123        }
1124
1125        strbuf_release(&line);
1126}
1127
1128/*
1129 * Get the packed_ref_cache for the specified files_ref_store,
1130 * creating it if necessary.
1131 */
1132static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *refs)
1133{
1134        char *packed_refs_file;
1135
1136        if (*refs->base.submodule)
1137                packed_refs_file = git_pathdup_submodule(refs->base.submodule,
1138                                                         "packed-refs");
1139        else
1140                packed_refs_file = git_pathdup("packed-refs");
1141
1142        if (refs->packed &&
1143            !stat_validity_check(&refs->packed->validity, packed_refs_file))
1144                clear_packed_ref_cache(refs);
1145
1146        if (!refs->packed) {
1147                FILE *f;
1148
1149                refs->packed = xcalloc(1, sizeof(*refs->packed));
1150                acquire_packed_ref_cache(refs->packed);
1151                refs->packed->root = create_dir_entry(refs, "", 0, 0);
1152                f = fopen(packed_refs_file, "r");
1153                if (f) {
1154                        stat_validity_update(&refs->packed->validity, fileno(f));
1155                        read_packed_refs(f, get_ref_dir(refs->packed->root));
1156                        fclose(f);
1157                }
1158        }
1159        free(packed_refs_file);
1160        return refs->packed;
1161}
1162
1163static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_cache)
1164{
1165        return get_ref_dir(packed_ref_cache->root);
1166}
1167
1168static struct ref_dir *get_packed_refs(struct files_ref_store *refs)
1169{
1170        return get_packed_ref_dir(get_packed_ref_cache(refs));
1171}
1172
1173/*
1174 * Add a reference to the in-memory packed reference cache.  This may
1175 * only be called while the packed-refs file is locked (see
1176 * lock_packed_refs()).  To actually write the packed-refs file, call
1177 * commit_packed_refs().
1178 */
1179static void add_packed_ref(struct files_ref_store *refs,
1180                           const char *refname, const unsigned char *sha1)
1181{
1182        struct packed_ref_cache *packed_ref_cache = get_packed_ref_cache(refs);
1183
1184        if (!packed_ref_cache->lock)
1185                die("internal error: packed refs not locked");
1186        add_ref(get_packed_ref_dir(packed_ref_cache),
1187                create_ref_entry(refname, sha1, REF_ISPACKED, 1));
1188}
1189
1190/*
1191 * Read the loose references from the namespace dirname into dir
1192 * (without recursing).  dirname must end with '/'.  dir must be the
1193 * directory entry corresponding to dirname.
1194 */
1195static void read_loose_refs(const char *dirname, struct ref_dir *dir)
1196{
1197        struct files_ref_store *refs = dir->ref_store;
1198        DIR *d;
1199        struct dirent *de;
1200        int dirnamelen = strlen(dirname);
1201        struct strbuf refname;
1202        struct strbuf path = STRBUF_INIT;
1203        size_t path_baselen;
1204        int err = 0;
1205
1206        if (*refs->base.submodule)
1207                err = strbuf_git_path_submodule(&path, refs->base.submodule, "%s", dirname);
1208        else
1209                strbuf_git_path(&path, "%s", dirname);
1210        path_baselen = path.len;
1211
1212        if (err) {
1213                strbuf_release(&path);
1214                return;
1215        }
1216
1217        d = opendir(path.buf);
1218        if (!d) {
1219                strbuf_release(&path);
1220                return;
1221        }
1222
1223        strbuf_init(&refname, dirnamelen + 257);
1224        strbuf_add(&refname, dirname, dirnamelen);
1225
1226        while ((de = readdir(d)) != NULL) {
1227                unsigned char sha1[20];
1228                struct stat st;
1229                int flag;
1230
1231                if (de->d_name[0] == '.')
1232                        continue;
1233                if (ends_with(de->d_name, ".lock"))
1234                        continue;
1235                strbuf_addstr(&refname, de->d_name);
1236                strbuf_addstr(&path, de->d_name);
1237                if (stat(path.buf, &st) < 0) {
1238                        ; /* silently ignore */
1239                } else if (S_ISDIR(st.st_mode)) {
1240                        strbuf_addch(&refname, '/');
1241                        add_entry_to_dir(dir,
1242                                         create_dir_entry(refs, refname.buf,
1243                                                          refname.len, 1));
1244                } else {
1245                        int read_ok;
1246
1247                        if (*refs->base.submodule) {
1248                                hashclr(sha1);
1249                                flag = 0;
1250                                read_ok = !resolve_gitlink_ref(refs->base.submodule,
1251                                                               refname.buf, sha1);
1252                        } else {
1253                                read_ok = !read_ref_full(refname.buf,
1254                                                         RESOLVE_REF_READING,
1255                                                         sha1, &flag);
1256                        }
1257
1258                        if (!read_ok) {
1259                                hashclr(sha1);
1260                                flag |= REF_ISBROKEN;
1261                        } else if (is_null_sha1(sha1)) {
1262                                /*
1263                                 * It is so astronomically unlikely
1264                                 * that NULL_SHA1 is the SHA-1 of an
1265                                 * actual object that we consider its
1266                                 * appearance in a loose reference
1267                                 * file to be repo corruption
1268                                 * (probably due to a software bug).
1269                                 */
1270                                flag |= REF_ISBROKEN;
1271                        }
1272
1273                        if (check_refname_format(refname.buf,
1274                                                 REFNAME_ALLOW_ONELEVEL)) {
1275                                if (!refname_is_safe(refname.buf))
1276                                        die("loose refname is dangerous: %s", refname.buf);
1277                                hashclr(sha1);
1278                                flag |= REF_BAD_NAME | REF_ISBROKEN;
1279                        }
1280                        add_entry_to_dir(dir,
1281                                         create_ref_entry(refname.buf, sha1, flag, 0));
1282                }
1283                strbuf_setlen(&refname, dirnamelen);
1284                strbuf_setlen(&path, path_baselen);
1285        }
1286        strbuf_release(&refname);
1287        strbuf_release(&path);
1288        closedir(d);
1289}
1290
1291static struct ref_dir *get_loose_refs(struct files_ref_store *refs)
1292{
1293        if (!refs->loose) {
1294                /*
1295                 * Mark the top-level directory complete because we
1296                 * are about to read the only subdirectory that can
1297                 * hold references:
1298                 */
1299                refs->loose = create_dir_entry(refs, "", 0, 0);
1300                /*
1301                 * Create an incomplete entry for "refs/":
1302                 */
1303                add_entry_to_dir(get_ref_dir(refs->loose),
1304                                 create_dir_entry(refs, "refs/", 5, 1));
1305        }
1306        return get_ref_dir(refs->loose);
1307}
1308
1309/*
1310 * Return the ref_entry for the given refname from the packed
1311 * references.  If it does not exist, return NULL.
1312 */
1313static struct ref_entry *get_packed_ref(struct files_ref_store *refs,
1314                                        const char *refname)
1315{
1316        return find_ref(get_packed_refs(refs), refname);
1317}
1318
1319/*
1320 * A loose ref file doesn't exist; check for a packed ref.
1321 */
1322static int resolve_packed_ref(struct files_ref_store *refs,
1323                              const char *refname,
1324                              unsigned char *sha1, unsigned int *flags)
1325{
1326        struct ref_entry *entry;
1327
1328        /*
1329         * The loose reference file does not exist; check for a packed
1330         * reference.
1331         */
1332        entry = get_packed_ref(refs, refname);
1333        if (entry) {
1334                hashcpy(sha1, entry->u.value.oid.hash);
1335                *flags |= REF_ISPACKED;
1336                return 0;
1337        }
1338        /* refname is not a packed reference. */
1339        return -1;
1340}
1341
1342static int files_read_raw_ref(struct ref_store *ref_store,
1343                              const char *refname, unsigned char *sha1,
1344                              struct strbuf *referent, unsigned int *type)
1345{
1346        struct files_ref_store *refs =
1347                files_downcast(ref_store, 1, "read_raw_ref");
1348        struct strbuf sb_contents = STRBUF_INIT;
1349        struct strbuf sb_path = STRBUF_INIT;
1350        const char *path;
1351        const char *buf;
1352        struct stat st;
1353        int fd;
1354        int ret = -1;
1355        int save_errno;
1356        int remaining_retries = 3;
1357
1358        *type = 0;
1359        strbuf_reset(&sb_path);
1360
1361        if (*refs->base.submodule)
1362                strbuf_git_path_submodule(&sb_path, refs->base.submodule, "%s", refname);
1363        else
1364                strbuf_git_path(&sb_path, "%s", refname);
1365
1366        path = sb_path.buf;
1367
1368stat_ref:
1369        /*
1370         * We might have to loop back here to avoid a race
1371         * condition: first we lstat() the file, then we try
1372         * to read it as a link or as a file.  But if somebody
1373         * changes the type of the file (file <-> directory
1374         * <-> symlink) between the lstat() and reading, then
1375         * we don't want to report that as an error but rather
1376         * try again starting with the lstat().
1377         *
1378         * We'll keep a count of the retries, though, just to avoid
1379         * any confusing situation sending us into an infinite loop.
1380         */
1381
1382        if (remaining_retries-- <= 0)
1383                goto out;
1384
1385        if (lstat(path, &st) < 0) {
1386                if (errno != ENOENT)
1387                        goto out;
1388                if (resolve_packed_ref(refs, refname, sha1, type)) {
1389                        errno = ENOENT;
1390                        goto out;
1391                }
1392                ret = 0;
1393                goto out;
1394        }
1395
1396        /* Follow "normalized" - ie "refs/.." symlinks by hand */
1397        if (S_ISLNK(st.st_mode)) {
1398                strbuf_reset(&sb_contents);
1399                if (strbuf_readlink(&sb_contents, path, 0) < 0) {
1400                        if (errno == ENOENT || errno == EINVAL)
1401                                /* inconsistent with lstat; retry */
1402                                goto stat_ref;
1403                        else
1404                                goto out;
1405                }
1406                if (starts_with(sb_contents.buf, "refs/") &&
1407                    !check_refname_format(sb_contents.buf, 0)) {
1408                        strbuf_swap(&sb_contents, referent);
1409                        *type |= REF_ISSYMREF;
1410                        ret = 0;
1411                        goto out;
1412                }
1413                /*
1414                 * It doesn't look like a refname; fall through to just
1415                 * treating it like a non-symlink, and reading whatever it
1416                 * points to.
1417                 */
1418        }
1419
1420        /* Is it a directory? */
1421        if (S_ISDIR(st.st_mode)) {
1422                /*
1423                 * Even though there is a directory where the loose
1424                 * ref is supposed to be, there could still be a
1425                 * packed ref:
1426                 */
1427                if (resolve_packed_ref(refs, refname, sha1, type)) {
1428                        errno = EISDIR;
1429                        goto out;
1430                }
1431                ret = 0;
1432                goto out;
1433        }
1434
1435        /*
1436         * Anything else, just open it and try to use it as
1437         * a ref
1438         */
1439        fd = open(path, O_RDONLY);
1440        if (fd < 0) {
1441                if (errno == ENOENT && !S_ISLNK(st.st_mode))
1442                        /* inconsistent with lstat; retry */
1443                        goto stat_ref;
1444                else
1445                        goto out;
1446        }
1447        strbuf_reset(&sb_contents);
1448        if (strbuf_read(&sb_contents, fd, 256) < 0) {
1449                int save_errno = errno;
1450                close(fd);
1451                errno = save_errno;
1452                goto out;
1453        }
1454        close(fd);
1455        strbuf_rtrim(&sb_contents);
1456        buf = sb_contents.buf;
1457        if (starts_with(buf, "ref:")) {
1458                buf += 4;
1459                while (isspace(*buf))
1460                        buf++;
1461
1462                strbuf_reset(referent);
1463                strbuf_addstr(referent, buf);
1464                *type |= REF_ISSYMREF;
1465                ret = 0;
1466                goto out;
1467        }
1468
1469        /*
1470         * Please note that FETCH_HEAD has additional
1471         * data after the sha.
1472         */
1473        if (get_sha1_hex(buf, sha1) ||
1474            (buf[40] != '\0' && !isspace(buf[40]))) {
1475                *type |= REF_ISBROKEN;
1476                errno = EINVAL;
1477                goto out;
1478        }
1479
1480        ret = 0;
1481
1482out:
1483        save_errno = errno;
1484        strbuf_release(&sb_path);
1485        strbuf_release(&sb_contents);
1486        errno = save_errno;
1487        return ret;
1488}
1489
1490static void unlock_ref(struct ref_lock *lock)
1491{
1492        /* Do not free lock->lk -- atexit() still looks at them */
1493        if (lock->lk)
1494                rollback_lock_file(lock->lk);
1495        free(lock->ref_name);
1496        free(lock);
1497}
1498
1499/*
1500 * Lock refname, without following symrefs, and set *lock_p to point
1501 * at a newly-allocated lock object. Fill in lock->old_oid, referent,
1502 * and type similarly to read_raw_ref().
1503 *
1504 * The caller must verify that refname is a "safe" reference name (in
1505 * the sense of refname_is_safe()) before calling this function.
1506 *
1507 * If the reference doesn't already exist, verify that refname doesn't
1508 * have a D/F conflict with any existing references. extras and skip
1509 * are passed to verify_refname_available_dir() for this check.
1510 *
1511 * If mustexist is not set and the reference is not found or is
1512 * broken, lock the reference anyway but clear sha1.
1513 *
1514 * Return 0 on success. On failure, write an error message to err and
1515 * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
1516 *
1517 * Implementation note: This function is basically
1518 *
1519 *     lock reference
1520 *     read_raw_ref()
1521 *
1522 * but it includes a lot more code to
1523 * - Deal with possible races with other processes
1524 * - Avoid calling verify_refname_available_dir() when it can be
1525 *   avoided, namely if we were successfully able to read the ref
1526 * - Generate informative error messages in the case of failure
1527 */
1528static int lock_raw_ref(struct files_ref_store *refs,
1529                        const char *refname, int mustexist,
1530                        const struct string_list *extras,
1531                        const struct string_list *skip,
1532                        struct ref_lock **lock_p,
1533                        struct strbuf *referent,
1534                        unsigned int *type,
1535                        struct strbuf *err)
1536{
1537        struct ref_lock *lock;
1538        struct strbuf ref_file = STRBUF_INIT;
1539        int attempts_remaining = 3;
1540        int ret = TRANSACTION_GENERIC_ERROR;
1541
1542        assert(err);
1543        assert_main_repository(&refs->base, "lock_raw_ref");
1544
1545        *type = 0;
1546
1547        /* First lock the file so it can't change out from under us. */
1548
1549        *lock_p = lock = xcalloc(1, sizeof(*lock));
1550
1551        lock->ref_name = xstrdup(refname);
1552        strbuf_git_path(&ref_file, "%s", refname);
1553
1554retry:
1555        switch (safe_create_leading_directories(ref_file.buf)) {
1556        case SCLD_OK:
1557                break; /* success */
1558        case SCLD_EXISTS:
1559                /*
1560                 * Suppose refname is "refs/foo/bar". We just failed
1561                 * to create the containing directory, "refs/foo",
1562                 * because there was a non-directory in the way. This
1563                 * indicates a D/F conflict, probably because of
1564                 * another reference such as "refs/foo". There is no
1565                 * reason to expect this error to be transitory.
1566                 */
1567                if (verify_refname_available(refname, extras, skip, err)) {
1568                        if (mustexist) {
1569                                /*
1570                                 * To the user the relevant error is
1571                                 * that the "mustexist" reference is
1572                                 * missing:
1573                                 */
1574                                strbuf_reset(err);
1575                                strbuf_addf(err, "unable to resolve reference '%s'",
1576                                            refname);
1577                        } else {
1578                                /*
1579                                 * The error message set by
1580                                 * verify_refname_available_dir() is OK.
1581                                 */
1582                                ret = TRANSACTION_NAME_CONFLICT;
1583                        }
1584                } else {
1585                        /*
1586                         * The file that is in the way isn't a loose
1587                         * reference. Report it as a low-level
1588                         * failure.
1589                         */
1590                        strbuf_addf(err, "unable to create lock file %s.lock; "
1591                                    "non-directory in the way",
1592                                    ref_file.buf);
1593                }
1594                goto error_return;
1595        case SCLD_VANISHED:
1596                /* Maybe another process was tidying up. Try again. */
1597                if (--attempts_remaining > 0)
1598                        goto retry;
1599                /* fall through */
1600        default:
1601                strbuf_addf(err, "unable to create directory for %s",
1602                            ref_file.buf);
1603                goto error_return;
1604        }
1605
1606        if (!lock->lk)
1607                lock->lk = xcalloc(1, sizeof(struct lock_file));
1608
1609        if (hold_lock_file_for_update(lock->lk, ref_file.buf, LOCK_NO_DEREF) < 0) {
1610                if (errno == ENOENT && --attempts_remaining > 0) {
1611                        /*
1612                         * Maybe somebody just deleted one of the
1613                         * directories leading to ref_file.  Try
1614                         * again:
1615                         */
1616                        goto retry;
1617                } else {
1618                        unable_to_lock_message(ref_file.buf, errno, err);
1619                        goto error_return;
1620                }
1621        }
1622
1623        /*
1624         * Now we hold the lock and can read the reference without
1625         * fear that its value will change.
1626         */
1627
1628        if (files_read_raw_ref(&refs->base, refname,
1629                               lock->old_oid.hash, referent, type)) {
1630                if (errno == ENOENT) {
1631                        if (mustexist) {
1632                                /* Garden variety missing reference. */
1633                                strbuf_addf(err, "unable to resolve reference '%s'",
1634                                            refname);
1635                                goto error_return;
1636                        } else {
1637                                /*
1638                                 * Reference is missing, but that's OK. We
1639                                 * know that there is not a conflict with
1640                                 * another loose reference because
1641                                 * (supposing that we are trying to lock
1642                                 * reference "refs/foo/bar"):
1643                                 *
1644                                 * - We were successfully able to create
1645                                 *   the lockfile refs/foo/bar.lock, so we
1646                                 *   know there cannot be a loose reference
1647                                 *   named "refs/foo".
1648                                 *
1649                                 * - We got ENOENT and not EISDIR, so we
1650                                 *   know that there cannot be a loose
1651                                 *   reference named "refs/foo/bar/baz".
1652                                 */
1653                        }
1654                } else if (errno == EISDIR) {
1655                        /*
1656                         * There is a directory in the way. It might have
1657                         * contained references that have been deleted. If
1658                         * we don't require that the reference already
1659                         * exists, try to remove the directory so that it
1660                         * doesn't cause trouble when we want to rename the
1661                         * lockfile into place later.
1662                         */
1663                        if (mustexist) {
1664                                /* Garden variety missing reference. */
1665                                strbuf_addf(err, "unable to resolve reference '%s'",
1666                                            refname);
1667                                goto error_return;
1668                        } else if (remove_dir_recursively(&ref_file,
1669                                                          REMOVE_DIR_EMPTY_ONLY)) {
1670                                if (verify_refname_available_dir(
1671                                                    refname, extras, skip,
1672                                                    get_loose_refs(refs),
1673                                                    err)) {
1674                                        /*
1675                                         * The error message set by
1676                                         * verify_refname_available() is OK.
1677                                         */
1678                                        ret = TRANSACTION_NAME_CONFLICT;
1679                                        goto error_return;
1680                                } else {
1681                                        /*
1682                                         * We can't delete the directory,
1683                                         * but we also don't know of any
1684                                         * references that it should
1685                                         * contain.
1686                                         */
1687                                        strbuf_addf(err, "there is a non-empty directory '%s' "
1688                                                    "blocking reference '%s'",
1689                                                    ref_file.buf, refname);
1690                                        goto error_return;
1691                                }
1692                        }
1693                } else if (errno == EINVAL && (*type & REF_ISBROKEN)) {
1694                        strbuf_addf(err, "unable to resolve reference '%s': "
1695                                    "reference broken", refname);
1696                        goto error_return;
1697                } else {
1698                        strbuf_addf(err, "unable to resolve reference '%s': %s",
1699                                    refname, strerror(errno));
1700                        goto error_return;
1701                }
1702
1703                /*
1704                 * If the ref did not exist and we are creating it,
1705                 * make sure there is no existing packed ref whose
1706                 * name begins with our refname, nor a packed ref
1707                 * whose name is a proper prefix of our refname.
1708                 */
1709                if (verify_refname_available_dir(
1710                                    refname, extras, skip,
1711                                    get_packed_refs(refs),
1712                                    err)) {
1713                        goto error_return;
1714                }
1715        }
1716
1717        ret = 0;
1718        goto out;
1719
1720error_return:
1721        unlock_ref(lock);
1722        *lock_p = NULL;
1723
1724out:
1725        strbuf_release(&ref_file);
1726        return ret;
1727}
1728
1729/*
1730 * Peel the entry (if possible) and return its new peel_status.  If
1731 * repeel is true, re-peel the entry even if there is an old peeled
1732 * value that is already stored in it.
1733 *
1734 * It is OK to call this function with a packed reference entry that
1735 * might be stale and might even refer to an object that has since
1736 * been garbage-collected.  In such a case, if the entry has
1737 * REF_KNOWS_PEELED then leave the status unchanged and return
1738 * PEEL_PEELED or PEEL_NON_TAG; otherwise, return PEEL_INVALID.
1739 */
1740static enum peel_status peel_entry(struct ref_entry *entry, int repeel)
1741{
1742        enum peel_status status;
1743
1744        if (entry->flag & REF_KNOWS_PEELED) {
1745                if (repeel) {
1746                        entry->flag &= ~REF_KNOWS_PEELED;
1747                        oidclr(&entry->u.value.peeled);
1748                } else {
1749                        return is_null_oid(&entry->u.value.peeled) ?
1750                                PEEL_NON_TAG : PEEL_PEELED;
1751                }
1752        }
1753        if (entry->flag & REF_ISBROKEN)
1754                return PEEL_BROKEN;
1755        if (entry->flag & REF_ISSYMREF)
1756                return PEEL_IS_SYMREF;
1757
1758        status = peel_object(entry->u.value.oid.hash, entry->u.value.peeled.hash);
1759        if (status == PEEL_PEELED || status == PEEL_NON_TAG)
1760                entry->flag |= REF_KNOWS_PEELED;
1761        return status;
1762}
1763
1764static int files_peel_ref(struct ref_store *ref_store,
1765                          const char *refname, unsigned char *sha1)
1766{
1767        struct files_ref_store *refs = files_downcast(ref_store, 0, "peel_ref");
1768        int flag;
1769        unsigned char base[20];
1770
1771        if (current_ref_iter && current_ref_iter->refname == refname) {
1772                struct object_id peeled;
1773
1774                if (ref_iterator_peel(current_ref_iter, &peeled))
1775                        return -1;
1776                hashcpy(sha1, peeled.hash);
1777                return 0;
1778        }
1779
1780        if (read_ref_full(refname, RESOLVE_REF_READING, base, &flag))
1781                return -1;
1782
1783        /*
1784         * If the reference is packed, read its ref_entry from the
1785         * cache in the hope that we already know its peeled value.
1786         * We only try this optimization on packed references because
1787         * (a) forcing the filling of the loose reference cache could
1788         * be expensive and (b) loose references anyway usually do not
1789         * have REF_KNOWS_PEELED.
1790         */
1791        if (flag & REF_ISPACKED) {
1792                struct ref_entry *r = get_packed_ref(refs, refname);
1793                if (r) {
1794                        if (peel_entry(r, 0))
1795                                return -1;
1796                        hashcpy(sha1, r->u.value.peeled.hash);
1797                        return 0;
1798                }
1799        }
1800
1801        return peel_object(base, sha1);
1802}
1803
1804struct files_ref_iterator {
1805        struct ref_iterator base;
1806
1807        struct packed_ref_cache *packed_ref_cache;
1808        struct ref_iterator *iter0;
1809        unsigned int flags;
1810};
1811
1812static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
1813{
1814        struct files_ref_iterator *iter =
1815                (struct files_ref_iterator *)ref_iterator;
1816        int ok;
1817
1818        while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
1819                if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
1820                    ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
1821                        continue;
1822
1823                if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
1824                    !ref_resolves_to_object(iter->iter0->refname,
1825                                            iter->iter0->oid,
1826                                            iter->iter0->flags))
1827                        continue;
1828
1829                iter->base.refname = iter->iter0->refname;
1830                iter->base.oid = iter->iter0->oid;
1831                iter->base.flags = iter->iter0->flags;
1832                return ITER_OK;
1833        }
1834
1835        iter->iter0 = NULL;
1836        if (ref_iterator_abort(ref_iterator) != ITER_DONE)
1837                ok = ITER_ERROR;
1838
1839        return ok;
1840}
1841
1842static int files_ref_iterator_peel(struct ref_iterator *ref_iterator,
1843                                   struct object_id *peeled)
1844{
1845        struct files_ref_iterator *iter =
1846                (struct files_ref_iterator *)ref_iterator;
1847
1848        return ref_iterator_peel(iter->iter0, peeled);
1849}
1850
1851static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
1852{
1853        struct files_ref_iterator *iter =
1854                (struct files_ref_iterator *)ref_iterator;
1855        int ok = ITER_DONE;
1856
1857        if (iter->iter0)
1858                ok = ref_iterator_abort(iter->iter0);
1859
1860        release_packed_ref_cache(iter->packed_ref_cache);
1861        base_ref_iterator_free(ref_iterator);
1862        return ok;
1863}
1864
1865static struct ref_iterator_vtable files_ref_iterator_vtable = {
1866        files_ref_iterator_advance,
1867        files_ref_iterator_peel,
1868        files_ref_iterator_abort
1869};
1870
1871static struct ref_iterator *files_ref_iterator_begin(
1872                struct ref_store *ref_store,
1873                const char *prefix, unsigned int flags)
1874{
1875        struct files_ref_store *refs =
1876                files_downcast(ref_store, 1, "ref_iterator_begin");
1877        struct ref_dir *loose_dir, *packed_dir;
1878        struct ref_iterator *loose_iter, *packed_iter;
1879        struct files_ref_iterator *iter;
1880        struct ref_iterator *ref_iterator;
1881
1882        if (!refs)
1883                return empty_ref_iterator_begin();
1884
1885        if (ref_paranoia < 0)
1886                ref_paranoia = git_env_bool("GIT_REF_PARANOIA", 0);
1887        if (ref_paranoia)
1888                flags |= DO_FOR_EACH_INCLUDE_BROKEN;
1889
1890        iter = xcalloc(1, sizeof(*iter));
1891        ref_iterator = &iter->base;
1892        base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable);
1893
1894        /*
1895         * We must make sure that all loose refs are read before
1896         * accessing the packed-refs file; this avoids a race
1897         * condition if loose refs are migrated to the packed-refs
1898         * file by a simultaneous process, but our in-memory view is
1899         * from before the migration. We ensure this as follows:
1900         * First, we call prime_ref_dir(), which pre-reads the loose
1901         * references for the subtree into the cache. (If they've
1902         * already been read, that's OK; we only need to guarantee
1903         * that they're read before the packed refs, not *how much*
1904         * before.) After that, we call get_packed_ref_cache(), which
1905         * internally checks whether the packed-ref cache is up to
1906         * date with what is on disk, and re-reads it if not.
1907         */
1908
1909        loose_dir = get_loose_refs(refs);
1910
1911        if (prefix && *prefix)
1912                loose_dir = find_containing_dir(loose_dir, prefix, 0);
1913
1914        if (loose_dir) {
1915                prime_ref_dir(loose_dir);
1916                loose_iter = cache_ref_iterator_begin(loose_dir);
1917        } else {
1918                /* There's nothing to iterate over. */
1919                loose_iter = empty_ref_iterator_begin();
1920        }
1921
1922        iter->packed_ref_cache = get_packed_ref_cache(refs);
1923        acquire_packed_ref_cache(iter->packed_ref_cache);
1924        packed_dir = get_packed_ref_dir(iter->packed_ref_cache);
1925
1926        if (prefix && *prefix)
1927                packed_dir = find_containing_dir(packed_dir, prefix, 0);
1928
1929        if (packed_dir) {
1930                packed_iter = cache_ref_iterator_begin(packed_dir);
1931        } else {
1932                /* There's nothing to iterate over. */
1933                packed_iter = empty_ref_iterator_begin();
1934        }
1935
1936        iter->iter0 = overlay_ref_iterator_begin(loose_iter, packed_iter);
1937        iter->flags = flags;
1938
1939        return ref_iterator;
1940}
1941
1942/*
1943 * Verify that the reference locked by lock has the value old_sha1.
1944 * Fail if the reference doesn't exist and mustexist is set. Return 0
1945 * on success. On error, write an error message to err, set errno, and
1946 * return a negative value.
1947 */
1948static int verify_lock(struct ref_lock *lock,
1949                       const unsigned char *old_sha1, int mustexist,
1950                       struct strbuf *err)
1951{
1952        assert(err);
1953
1954        if (read_ref_full(lock->ref_name,
1955                          mustexist ? RESOLVE_REF_READING : 0,
1956                          lock->old_oid.hash, NULL)) {
1957                if (old_sha1) {
1958                        int save_errno = errno;
1959                        strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
1960                        errno = save_errno;
1961                        return -1;
1962                } else {
1963                        oidclr(&lock->old_oid);
1964                        return 0;
1965                }
1966        }
1967        if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
1968                strbuf_addf(err, "ref '%s' is at %s but expected %s",
1969                            lock->ref_name,
1970                            oid_to_hex(&lock->old_oid),
1971                            sha1_to_hex(old_sha1));
1972                errno = EBUSY;
1973                return -1;
1974        }
1975        return 0;
1976}
1977
1978static int remove_empty_directories(struct strbuf *path)
1979{
1980        /*
1981         * we want to create a file but there is a directory there;
1982         * if that is an empty directory (or a directory that contains
1983         * only empty directories), remove them.
1984         */
1985        return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
1986}
1987
1988static int create_reflock(const char *path, void *cb)
1989{
1990        struct lock_file *lk = cb;
1991
1992        return hold_lock_file_for_update(lk, path, LOCK_NO_DEREF) < 0 ? -1 : 0;
1993}
1994
1995/*
1996 * Locks a ref returning the lock on success and NULL on failure.
1997 * On failure errno is set to something meaningful.
1998 */
1999static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
2000                                            const char *refname,
2001                                            const unsigned char *old_sha1,
2002                                            const struct string_list *extras,
2003                                            const struct string_list *skip,
2004                                            unsigned int flags, int *type,
2005                                            struct strbuf *err)
2006{
2007        struct strbuf ref_file = STRBUF_INIT;
2008        struct ref_lock *lock;
2009        int last_errno = 0;
2010        int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
2011        int resolve_flags = RESOLVE_REF_NO_RECURSE;
2012        int resolved;
2013
2014        assert_main_repository(&refs->base, "lock_ref_sha1_basic");
2015        assert(err);
2016
2017        lock = xcalloc(1, sizeof(struct ref_lock));
2018
2019        if (mustexist)
2020                resolve_flags |= RESOLVE_REF_READING;
2021        if (flags & REF_DELETING)
2022                resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
2023
2024        strbuf_git_path(&ref_file, "%s", refname);
2025        resolved = !!resolve_ref_unsafe(refname, resolve_flags,
2026                                        lock->old_oid.hash, type);
2027        if (!resolved && errno == EISDIR) {
2028                /*
2029                 * we are trying to lock foo but we used to
2030                 * have foo/bar which now does not exist;
2031                 * it is normal for the empty directory 'foo'
2032                 * to remain.
2033                 */
2034                if (remove_empty_directories(&ref_file)) {
2035                        last_errno = errno;
2036                        if (!verify_refname_available_dir(
2037                                            refname, extras, skip,
2038                                            get_loose_refs(refs), err))
2039                                strbuf_addf(err, "there are still refs under '%s'",
2040                                            refname);
2041                        goto error_return;
2042                }
2043                resolved = !!resolve_ref_unsafe(refname, resolve_flags,
2044                                                lock->old_oid.hash, type);
2045        }
2046        if (!resolved) {
2047                last_errno = errno;
2048                if (last_errno != ENOTDIR ||
2049                    !verify_refname_available_dir(
2050                                    refname, extras, skip,
2051                                    get_loose_refs(refs), err))
2052                        strbuf_addf(err, "unable to resolve reference '%s': %s",
2053                                    refname, strerror(last_errno));
2054
2055                goto error_return;
2056        }
2057
2058        /*
2059         * If the ref did not exist and we are creating it, make sure
2060         * there is no existing packed ref whose name begins with our
2061         * refname, nor a packed ref whose name is a proper prefix of
2062         * our refname.
2063         */
2064        if (is_null_oid(&lock->old_oid) &&
2065            verify_refname_available_dir(refname, extras, skip,
2066                                         get_packed_refs(refs),
2067                                         err)) {
2068                last_errno = ENOTDIR;
2069                goto error_return;
2070        }
2071
2072        lock->lk = xcalloc(1, sizeof(struct lock_file));
2073
2074        lock->ref_name = xstrdup(refname);
2075
2076        if (raceproof_create_file(ref_file.buf, create_reflock, lock->lk)) {
2077                last_errno = errno;
2078                unable_to_lock_message(ref_file.buf, errno, err);
2079                goto error_return;
2080        }
2081
2082        if (verify_lock(lock, old_sha1, mustexist, err)) {
2083                last_errno = errno;
2084                goto error_return;
2085        }
2086        goto out;
2087
2088 error_return:
2089        unlock_ref(lock);
2090        lock = NULL;
2091
2092 out:
2093        strbuf_release(&ref_file);
2094        errno = last_errno;
2095        return lock;
2096}
2097
2098/*
2099 * Write an entry to the packed-refs file for the specified refname.
2100 * If peeled is non-NULL, write it as the entry's peeled value.
2101 */
2102static void write_packed_entry(FILE *fh, char *refname, unsigned char *sha1,
2103                               unsigned char *peeled)
2104{
2105        fprintf_or_die(fh, "%s %s\n", sha1_to_hex(sha1), refname);
2106        if (peeled)
2107                fprintf_or_die(fh, "^%s\n", sha1_to_hex(peeled));
2108}
2109
2110/*
2111 * An each_ref_entry_fn that writes the entry to a packed-refs file.
2112 */
2113static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
2114{
2115        enum peel_status peel_status = peel_entry(entry, 0);
2116
2117        if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
2118                error("internal error: %s is not a valid packed reference!",
2119                      entry->name);
2120        write_packed_entry(cb_data, entry->name, entry->u.value.oid.hash,
2121                           peel_status == PEEL_PEELED ?
2122                           entry->u.value.peeled.hash : NULL);
2123        return 0;
2124}
2125
2126/*
2127 * Lock the packed-refs file for writing. Flags is passed to
2128 * hold_lock_file_for_update(). Return 0 on success. On errors, set
2129 * errno appropriately and return a nonzero value.
2130 */
2131static int lock_packed_refs(struct files_ref_store *refs, int flags)
2132{
2133        static int timeout_configured = 0;
2134        static int timeout_value = 1000;
2135        struct packed_ref_cache *packed_ref_cache;
2136
2137        assert_main_repository(&refs->base, "lock_packed_refs");
2138
2139        if (!timeout_configured) {
2140                git_config_get_int("core.packedrefstimeout", &timeout_value);
2141                timeout_configured = 1;
2142        }
2143
2144        if (hold_lock_file_for_update_timeout(
2145                            &packlock, git_path("packed-refs"),
2146                            flags, timeout_value) < 0)
2147                return -1;
2148        /*
2149         * Get the current packed-refs while holding the lock.  If the
2150         * packed-refs file has been modified since we last read it,
2151         * this will automatically invalidate the cache and re-read
2152         * the packed-refs file.
2153         */
2154        packed_ref_cache = get_packed_ref_cache(refs);
2155        packed_ref_cache->lock = &packlock;
2156        /* Increment the reference count to prevent it from being freed: */
2157        acquire_packed_ref_cache(packed_ref_cache);
2158        return 0;
2159}
2160
2161/*
2162 * Write the current version of the packed refs cache from memory to
2163 * disk. The packed-refs file must already be locked for writing (see
2164 * lock_packed_refs()). Return zero on success. On errors, set errno
2165 * and return a nonzero value
2166 */
2167static int commit_packed_refs(struct files_ref_store *refs)
2168{
2169        struct packed_ref_cache *packed_ref_cache =
2170                get_packed_ref_cache(refs);
2171        int error = 0;
2172        int save_errno = 0;
2173        FILE *out;
2174
2175        assert_main_repository(&refs->base, "commit_packed_refs");
2176
2177        if (!packed_ref_cache->lock)
2178                die("internal error: packed-refs not locked");
2179
2180        out = fdopen_lock_file(packed_ref_cache->lock, "w");
2181        if (!out)
2182                die_errno("unable to fdopen packed-refs descriptor");
2183
2184        fprintf_or_die(out, "%s", PACKED_REFS_HEADER);
2185        do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
2186                                 0, write_packed_entry_fn, out);
2187
2188        if (commit_lock_file(packed_ref_cache->lock)) {
2189                save_errno = errno;
2190                error = -1;
2191        }
2192        packed_ref_cache->lock = NULL;
2193        release_packed_ref_cache(packed_ref_cache);
2194        errno = save_errno;
2195        return error;
2196}
2197
2198/*
2199 * Rollback the lockfile for the packed-refs file, and discard the
2200 * in-memory packed reference cache.  (The packed-refs file will be
2201 * read anew if it is needed again after this function is called.)
2202 */
2203static void rollback_packed_refs(struct files_ref_store *refs)
2204{
2205        struct packed_ref_cache *packed_ref_cache =
2206                get_packed_ref_cache(refs);
2207
2208        assert_main_repository(&refs->base, "rollback_packed_refs");
2209
2210        if (!packed_ref_cache->lock)
2211                die("internal error: packed-refs not locked");
2212        rollback_lock_file(packed_ref_cache->lock);
2213        packed_ref_cache->lock = NULL;
2214        release_packed_ref_cache(packed_ref_cache);
2215        clear_packed_ref_cache(refs);
2216}
2217
2218struct ref_to_prune {
2219        struct ref_to_prune *next;
2220        unsigned char sha1[20];
2221        char name[FLEX_ARRAY];
2222};
2223
2224struct pack_refs_cb_data {
2225        unsigned int flags;
2226        struct ref_dir *packed_refs;
2227        struct ref_to_prune *ref_to_prune;
2228};
2229
2230/*
2231 * An each_ref_entry_fn that is run over loose references only.  If
2232 * the loose reference can be packed, add an entry in the packed ref
2233 * cache.  If the reference should be pruned, also add it to
2234 * ref_to_prune in the pack_refs_cb_data.
2235 */
2236static int pack_if_possible_fn(struct ref_entry *entry, void *cb_data)
2237{
2238        struct pack_refs_cb_data *cb = cb_data;
2239        enum peel_status peel_status;
2240        struct ref_entry *packed_entry;
2241        int is_tag_ref = starts_with(entry->name, "refs/tags/");
2242
2243        /* Do not pack per-worktree refs: */
2244        if (ref_type(entry->name) != REF_TYPE_NORMAL)
2245                return 0;
2246
2247        /* ALWAYS pack tags */
2248        if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref)
2249                return 0;
2250
2251        /* Do not pack symbolic or broken refs: */
2252        if ((entry->flag & REF_ISSYMREF) || !entry_resolves_to_object(entry))
2253                return 0;
2254
2255        /* Add a packed ref cache entry equivalent to the loose entry. */
2256        peel_status = peel_entry(entry, 1);
2257        if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
2258                die("internal error peeling reference %s (%s)",
2259                    entry->name, oid_to_hex(&entry->u.value.oid));
2260        packed_entry = find_ref(cb->packed_refs, entry->name);
2261        if (packed_entry) {
2262                /* Overwrite existing packed entry with info from loose entry */
2263                packed_entry->flag = REF_ISPACKED | REF_KNOWS_PEELED;
2264                oidcpy(&packed_entry->u.value.oid, &entry->u.value.oid);
2265        } else {
2266                packed_entry = create_ref_entry(entry->name, entry->u.value.oid.hash,
2267                                                REF_ISPACKED | REF_KNOWS_PEELED, 0);
2268                add_ref(cb->packed_refs, packed_entry);
2269        }
2270        oidcpy(&packed_entry->u.value.peeled, &entry->u.value.peeled);
2271
2272        /* Schedule the loose reference for pruning if requested. */
2273        if ((cb->flags & PACK_REFS_PRUNE)) {
2274                struct ref_to_prune *n;
2275                FLEX_ALLOC_STR(n, name, entry->name);
2276                hashcpy(n->sha1, entry->u.value.oid.hash);
2277                n->next = cb->ref_to_prune;
2278                cb->ref_to_prune = n;
2279        }
2280        return 0;
2281}
2282
2283enum {
2284        REMOVE_EMPTY_PARENTS_REF = 0x01,
2285        REMOVE_EMPTY_PARENTS_REFLOG = 0x02
2286};
2287
2288/*
2289 * Remove empty parent directories associated with the specified
2290 * reference and/or its reflog, but spare [logs/]refs/ and immediate
2291 * subdirs. flags is a combination of REMOVE_EMPTY_PARENTS_REF and/or
2292 * REMOVE_EMPTY_PARENTS_REFLOG.
2293 */
2294static void try_remove_empty_parents(const char *refname, unsigned int flags)
2295{
2296        struct strbuf buf = STRBUF_INIT;
2297        char *p, *q;
2298        int i;
2299
2300        strbuf_addstr(&buf, refname);
2301        p = buf.buf;
2302        for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
2303                while (*p && *p != '/')
2304                        p++;
2305                /* tolerate duplicate slashes; see check_refname_format() */
2306                while (*p == '/')
2307                        p++;
2308        }
2309        q = buf.buf + buf.len;
2310        while (flags & (REMOVE_EMPTY_PARENTS_REF | REMOVE_EMPTY_PARENTS_REFLOG)) {
2311                while (q > p && *q != '/')
2312                        q--;
2313                while (q > p && *(q-1) == '/')
2314                        q--;
2315                if (q == p)
2316                        break;
2317                strbuf_setlen(&buf, q - buf.buf);
2318                if ((flags & REMOVE_EMPTY_PARENTS_REF) &&
2319                    rmdir(git_path("%s", buf.buf)))
2320                        flags &= ~REMOVE_EMPTY_PARENTS_REF;
2321                if ((flags & REMOVE_EMPTY_PARENTS_REFLOG) &&
2322                    rmdir(git_path("logs/%s", buf.buf)))
2323                        flags &= ~REMOVE_EMPTY_PARENTS_REFLOG;
2324        }
2325        strbuf_release(&buf);
2326}
2327
2328/* make sure nobody touched the ref, and unlink */
2329static void prune_ref(struct ref_to_prune *r)
2330{
2331        struct ref_transaction *transaction;
2332        struct strbuf err = STRBUF_INIT;
2333
2334        if (check_refname_format(r->name, 0))
2335                return;
2336
2337        transaction = ref_transaction_begin(&err);
2338        if (!transaction ||
2339            ref_transaction_delete(transaction, r->name, r->sha1,
2340                                   REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
2341            ref_transaction_commit(transaction, &err)) {
2342                ref_transaction_free(transaction);
2343                error("%s", err.buf);
2344                strbuf_release(&err);
2345                return;
2346        }
2347        ref_transaction_free(transaction);
2348        strbuf_release(&err);
2349}
2350
2351static void prune_refs(struct ref_to_prune *r)
2352{
2353        while (r) {
2354                prune_ref(r);
2355                r = r->next;
2356        }
2357}
2358
2359static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
2360{
2361        struct files_ref_store *refs =
2362                files_downcast(ref_store, 0, "pack_refs");
2363        struct pack_refs_cb_data cbdata;
2364
2365        memset(&cbdata, 0, sizeof(cbdata));
2366        cbdata.flags = flags;
2367
2368        lock_packed_refs(refs, LOCK_DIE_ON_ERROR);
2369        cbdata.packed_refs = get_packed_refs(refs);
2370
2371        do_for_each_entry_in_dir(get_loose_refs(refs), 0,
2372                                 pack_if_possible_fn, &cbdata);
2373
2374        if (commit_packed_refs(refs))
2375                die_errno("unable to overwrite old ref-pack file");
2376
2377        prune_refs(cbdata.ref_to_prune);
2378        return 0;
2379}
2380
2381/*
2382 * Rewrite the packed-refs file, omitting any refs listed in
2383 * 'refnames'. On error, leave packed-refs unchanged, write an error
2384 * message to 'err', and return a nonzero value.
2385 *
2386 * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
2387 */
2388static int repack_without_refs(struct files_ref_store *refs,
2389                               struct string_list *refnames, struct strbuf *err)
2390{
2391        struct ref_dir *packed;
2392        struct string_list_item *refname;
2393        int ret, needs_repacking = 0, removed = 0;
2394
2395        assert_main_repository(&refs->base, "repack_without_refs");
2396        assert(err);
2397
2398        /* Look for a packed ref */
2399        for_each_string_list_item(refname, refnames) {
2400                if (get_packed_ref(refs, refname->string)) {
2401                        needs_repacking = 1;
2402                        break;
2403                }
2404        }
2405
2406        /* Avoid locking if we have nothing to do */
2407        if (!needs_repacking)
2408                return 0; /* no refname exists in packed refs */
2409
2410        if (lock_packed_refs(refs, 0)) {
2411                unable_to_lock_message(git_path("packed-refs"), errno, err);
2412                return -1;
2413        }
2414        packed = get_packed_refs(refs);
2415
2416        /* Remove refnames from the cache */
2417        for_each_string_list_item(refname, refnames)
2418                if (remove_entry(packed, refname->string) != -1)
2419                        removed = 1;
2420        if (!removed) {
2421                /*
2422                 * All packed entries disappeared while we were
2423                 * acquiring the lock.
2424                 */
2425                rollback_packed_refs(refs);
2426                return 0;
2427        }
2428
2429        /* Write what remains */
2430        ret = commit_packed_refs(refs);
2431        if (ret)
2432                strbuf_addf(err, "unable to overwrite old ref-pack file: %s",
2433                            strerror(errno));
2434        return ret;
2435}
2436
2437static int files_delete_refs(struct ref_store *ref_store,
2438                             struct string_list *refnames, unsigned int flags)
2439{
2440        struct files_ref_store *refs =
2441                files_downcast(ref_store, 0, "delete_refs");
2442        struct strbuf err = STRBUF_INIT;
2443        int i, result = 0;
2444
2445        if (!refnames->nr)
2446                return 0;
2447
2448        result = repack_without_refs(refs, refnames, &err);
2449        if (result) {
2450                /*
2451                 * If we failed to rewrite the packed-refs file, then
2452                 * it is unsafe to try to remove loose refs, because
2453                 * doing so might expose an obsolete packed value for
2454                 * a reference that might even point at an object that
2455                 * has been garbage collected.
2456                 */
2457                if (refnames->nr == 1)
2458                        error(_("could not delete reference %s: %s"),
2459                              refnames->items[0].string, err.buf);
2460                else
2461                        error(_("could not delete references: %s"), err.buf);
2462
2463                goto out;
2464        }
2465
2466        for (i = 0; i < refnames->nr; i++) {
2467                const char *refname = refnames->items[i].string;
2468
2469                if (delete_ref(refname, NULL, flags))
2470                        result |= error(_("could not remove reference %s"), refname);
2471        }
2472
2473out:
2474        strbuf_release(&err);
2475        return result;
2476}
2477
2478/*
2479 * People using contrib's git-new-workdir have .git/logs/refs ->
2480 * /some/other/path/.git/logs/refs, and that may live on another device.
2481 *
2482 * IOW, to avoid cross device rename errors, the temporary renamed log must
2483 * live into logs/refs.
2484 */
2485#define TMP_RENAMED_LOG  "logs/refs/.tmp-renamed-log"
2486
2487static int rename_tmp_log_callback(const char *path, void *cb)
2488{
2489        int *true_errno = cb;
2490
2491        if (rename(git_path(TMP_RENAMED_LOG), path)) {
2492                /*
2493                 * rename(a, b) when b is an existing directory ought
2494                 * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
2495                 * Sheesh. Record the true errno for error reporting,
2496                 * but report EISDIR to raceproof_create_file() so
2497                 * that it knows to retry.
2498                 */
2499                *true_errno = errno;
2500                if (errno == ENOTDIR)
2501                        errno = EISDIR;
2502                return -1;
2503        } else {
2504                return 0;
2505        }
2506}
2507
2508static int rename_tmp_log(const char *newrefname)
2509{
2510        char *path = git_pathdup("logs/%s", newrefname);
2511        int ret, true_errno;
2512
2513        ret = raceproof_create_file(path, rename_tmp_log_callback, &true_errno);
2514        if (ret) {
2515                if (errno == EISDIR)
2516                        error("directory not empty: %s", path);
2517                else
2518                        error("unable to move logfile %s to %s: %s",
2519                              git_path(TMP_RENAMED_LOG), path,
2520                              strerror(true_errno));
2521        }
2522
2523        free(path);
2524        return ret;
2525}
2526
2527static int files_verify_refname_available(struct ref_store *ref_store,
2528                                          const char *newname,
2529                                          const struct string_list *extras,
2530                                          const struct string_list *skip,
2531                                          struct strbuf *err)
2532{
2533        struct files_ref_store *refs =
2534                files_downcast(ref_store, 1, "verify_refname_available");
2535        struct ref_dir *packed_refs = get_packed_refs(refs);
2536        struct ref_dir *loose_refs = get_loose_refs(refs);
2537
2538        if (verify_refname_available_dir(newname, extras, skip,
2539                                         packed_refs, err) ||
2540            verify_refname_available_dir(newname, extras, skip,
2541                                         loose_refs, err))
2542                return -1;
2543
2544        return 0;
2545}
2546
2547static int write_ref_to_lockfile(struct ref_lock *lock,
2548                                 const unsigned char *sha1, struct strbuf *err);
2549static int commit_ref_update(struct files_ref_store *refs,
2550                             struct ref_lock *lock,
2551                             const unsigned char *sha1, const char *logmsg,
2552                             struct strbuf *err);
2553
2554static int files_rename_ref(struct ref_store *ref_store,
2555                            const char *oldrefname, const char *newrefname,
2556                            const char *logmsg)
2557{
2558        struct files_ref_store *refs =
2559                files_downcast(ref_store, 0, "rename_ref");
2560        unsigned char sha1[20], orig_sha1[20];
2561        int flag = 0, logmoved = 0;
2562        struct ref_lock *lock;
2563        struct stat loginfo;
2564        int log = !lstat(git_path("logs/%s", oldrefname), &loginfo);
2565        struct strbuf err = STRBUF_INIT;
2566
2567        if (log && S_ISLNK(loginfo.st_mode))
2568                return error("reflog for %s is a symlink", oldrefname);
2569
2570        if (!resolve_ref_unsafe(oldrefname, RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
2571                                orig_sha1, &flag))
2572                return error("refname %s not found", oldrefname);
2573
2574        if (flag & REF_ISSYMREF)
2575                return error("refname %s is a symbolic ref, renaming it is not supported",
2576                        oldrefname);
2577        if (!rename_ref_available(oldrefname, newrefname))
2578                return 1;
2579
2580        if (log && rename(git_path("logs/%s", oldrefname), git_path(TMP_RENAMED_LOG)))
2581                return error("unable to move logfile logs/%s to "TMP_RENAMED_LOG": %s",
2582                        oldrefname, strerror(errno));
2583
2584        if (delete_ref(oldrefname, orig_sha1, REF_NODEREF)) {
2585                error("unable to delete old %s", oldrefname);
2586                goto rollback;
2587        }
2588
2589        /*
2590         * Since we are doing a shallow lookup, sha1 is not the
2591         * correct value to pass to delete_ref as old_sha1. But that
2592         * doesn't matter, because an old_sha1 check wouldn't add to
2593         * the safety anyway; we want to delete the reference whatever
2594         * its current value.
2595         */
2596        if (!read_ref_full(newrefname, RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
2597                           sha1, NULL) &&
2598            delete_ref(newrefname, NULL, REF_NODEREF)) {
2599                if (errno == EISDIR) {
2600                        struct strbuf path = STRBUF_INIT;
2601                        int result;
2602
2603                        strbuf_git_path(&path, "%s", newrefname);
2604                        result = remove_empty_directories(&path);
2605                        strbuf_release(&path);
2606
2607                        if (result) {
2608                                error("Directory not empty: %s", newrefname);
2609                                goto rollback;
2610                        }
2611                } else {
2612                        error("unable to delete existing %s", newrefname);
2613                        goto rollback;
2614                }
2615        }
2616
2617        if (log && rename_tmp_log(newrefname))
2618                goto rollback;
2619
2620        logmoved = log;
2621
2622        lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
2623                                   REF_NODEREF, NULL, &err);
2624        if (!lock) {
2625                error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
2626                strbuf_release(&err);
2627                goto rollback;
2628        }
2629        hashcpy(lock->old_oid.hash, orig_sha1);
2630
2631        if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
2632            commit_ref_update(refs, lock, orig_sha1, logmsg, &err)) {
2633                error("unable to write current sha1 into %s: %s", newrefname, err.buf);
2634                strbuf_release(&err);
2635                goto rollback;
2636        }
2637
2638        return 0;
2639
2640 rollback:
2641        lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
2642                                   REF_NODEREF, NULL, &err);
2643        if (!lock) {
2644                error("unable to lock %s for rollback: %s", oldrefname, err.buf);
2645                strbuf_release(&err);
2646                goto rollbacklog;
2647        }
2648
2649        flag = log_all_ref_updates;
2650        log_all_ref_updates = LOG_REFS_NONE;
2651        if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
2652            commit_ref_update(refs, lock, orig_sha1, NULL, &err)) {
2653                error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
2654                strbuf_release(&err);
2655        }
2656        log_all_ref_updates = flag;
2657
2658 rollbacklog:
2659        if (logmoved && rename(git_path("logs/%s", newrefname), git_path("logs/%s", oldrefname)))
2660                error("unable to restore logfile %s from %s: %s",
2661                        oldrefname, newrefname, strerror(errno));
2662        if (!logmoved && log &&
2663            rename(git_path(TMP_RENAMED_LOG), git_path("logs/%s", oldrefname)))
2664                error("unable to restore logfile %s from "TMP_RENAMED_LOG": %s",
2665                        oldrefname, strerror(errno));
2666
2667        return 1;
2668}
2669
2670static int close_ref(struct ref_lock *lock)
2671{
2672        if (close_lock_file(lock->lk))
2673                return -1;
2674        return 0;
2675}
2676
2677static int commit_ref(struct ref_lock *lock)
2678{
2679        char *path = get_locked_file_path(lock->lk);
2680        struct stat st;
2681
2682        if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
2683                /*
2684                 * There is a directory at the path we want to rename
2685                 * the lockfile to. Hopefully it is empty; try to
2686                 * delete it.
2687                 */
2688                size_t len = strlen(path);
2689                struct strbuf sb_path = STRBUF_INIT;
2690
2691                strbuf_attach(&sb_path, path, len, len);
2692
2693                /*
2694                 * If this fails, commit_lock_file() will also fail
2695                 * and will report the problem.
2696                 */
2697                remove_empty_directories(&sb_path);
2698                strbuf_release(&sb_path);
2699        } else {
2700                free(path);
2701        }
2702
2703        if (commit_lock_file(lock->lk))
2704                return -1;
2705        return 0;
2706}
2707
2708static int open_or_create_logfile(const char *path, void *cb)
2709{
2710        int *fd = cb;
2711
2712        *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
2713        return (*fd < 0) ? -1 : 0;
2714}
2715
2716/*
2717 * Create a reflog for a ref. If force_create = 0, only create the
2718 * reflog for certain refs (those for which should_autocreate_reflog
2719 * returns non-zero). Otherwise, create it regardless of the reference
2720 * name. If the logfile already existed or was created, return 0 and
2721 * set *logfd to the file descriptor opened for appending to the file.
2722 * If no logfile exists and we decided not to create one, return 0 and
2723 * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
2724 * return -1.
2725 */
2726static int log_ref_setup(const char *refname, int force_create,
2727                         int *logfd, struct strbuf *err)
2728{
2729        char *logfile = git_pathdup("logs/%s", refname);
2730
2731        if (force_create || should_autocreate_reflog(refname)) {
2732                if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
2733                        if (errno == ENOENT)
2734                                strbuf_addf(err, "unable to create directory for '%s': "
2735                                            "%s", logfile, strerror(errno));
2736                        else if (errno == EISDIR)
2737                                strbuf_addf(err, "there are still logs under '%s'",
2738                                            logfile);
2739                        else
2740                                strbuf_addf(err, "unable to append to '%s': %s",
2741                                            logfile, strerror(errno));
2742
2743                        goto error;
2744                }
2745        } else {
2746                *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
2747                if (*logfd < 0) {
2748                        if (errno == ENOENT || errno == EISDIR) {
2749                                /*
2750                                 * The logfile doesn't already exist,
2751                                 * but that is not an error; it only
2752                                 * means that we won't write log
2753                                 * entries to it.
2754                                 */
2755                                ;
2756                        } else {
2757                                strbuf_addf(err, "unable to append to '%s': %s",
2758                                            logfile, strerror(errno));
2759                                goto error;
2760                        }
2761                }
2762        }
2763
2764        if (*logfd >= 0)
2765                adjust_shared_perm(logfile);
2766
2767        free(logfile);
2768        return 0;
2769
2770error:
2771        free(logfile);
2772        return -1;
2773}
2774
2775static int files_create_reflog(struct ref_store *ref_store,
2776                               const char *refname, int force_create,
2777                               struct strbuf *err)
2778{
2779        int fd;
2780
2781        /* Check validity (but we don't need the result): */
2782        files_downcast(ref_store, 0, "create_reflog");
2783
2784        if (log_ref_setup(refname, force_create, &fd, err))
2785                return -1;
2786
2787        if (fd >= 0)
2788                close(fd);
2789
2790        return 0;
2791}
2792
2793static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
2794                            const unsigned char *new_sha1,
2795                            const char *committer, const char *msg)
2796{
2797        int msglen, written;
2798        unsigned maxlen, len;
2799        char *logrec;
2800
2801        msglen = msg ? strlen(msg) : 0;
2802        maxlen = strlen(committer) + msglen + 100;
2803        logrec = xmalloc(maxlen);
2804        len = xsnprintf(logrec, maxlen, "%s %s %s\n",
2805                        sha1_to_hex(old_sha1),
2806                        sha1_to_hex(new_sha1),
2807                        committer);
2808        if (msglen)
2809                len += copy_reflog_msg(logrec + len - 1, msg) - 1;
2810
2811        written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
2812        free(logrec);
2813        if (written != len)
2814                return -1;
2815
2816        return 0;
2817}
2818
2819int files_log_ref_write(const char *refname, const unsigned char *old_sha1,
2820                        const unsigned char *new_sha1, const char *msg,
2821                        int flags, struct strbuf *err)
2822{
2823        int logfd, result;
2824
2825        if (log_all_ref_updates == LOG_REFS_UNSET)
2826                log_all_ref_updates = is_bare_repository() ? LOG_REFS_NONE : LOG_REFS_NORMAL;
2827
2828        result = log_ref_setup(refname, flags & REF_FORCE_CREATE_REFLOG,
2829                               &logfd, err);
2830
2831        if (result)
2832                return result;
2833
2834        if (logfd < 0)
2835                return 0;
2836        result = log_ref_write_fd(logfd, old_sha1, new_sha1,
2837                                  git_committer_info(0), msg);
2838        if (result) {
2839                int save_errno = errno;
2840
2841                strbuf_addf(err, "unable to append to '%s': %s",
2842                            git_path("logs/%s", refname), strerror(save_errno));
2843                close(logfd);
2844                return -1;
2845        }
2846        if (close(logfd)) {
2847                int save_errno = errno;
2848
2849                strbuf_addf(err, "unable to append to '%s': %s",
2850                            git_path("logs/%s", refname), strerror(save_errno));
2851                return -1;
2852        }
2853        return 0;
2854}
2855
2856/*
2857 * Write sha1 into the open lockfile, then close the lockfile. On
2858 * errors, rollback the lockfile, fill in *err and
2859 * return -1.
2860 */
2861static int write_ref_to_lockfile(struct ref_lock *lock,
2862                                 const unsigned char *sha1, struct strbuf *err)
2863{
2864        static char term = '\n';
2865        struct object *o;
2866        int fd;
2867
2868        o = parse_object(sha1);
2869        if (!o) {
2870                strbuf_addf(err,
2871                            "trying to write ref '%s' with nonexistent object %s",
2872                            lock->ref_name, sha1_to_hex(sha1));
2873                unlock_ref(lock);
2874                return -1;
2875        }
2876        if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
2877                strbuf_addf(err,
2878                            "trying to write non-commit object %s to branch '%s'",
2879                            sha1_to_hex(sha1), lock->ref_name);
2880                unlock_ref(lock);
2881                return -1;
2882        }
2883        fd = get_lock_file_fd(lock->lk);
2884        if (write_in_full(fd, sha1_to_hex(sha1), 40) != 40 ||
2885            write_in_full(fd, &term, 1) != 1 ||
2886            close_ref(lock) < 0) {
2887                strbuf_addf(err,
2888                            "couldn't write '%s'", get_lock_file_path(lock->lk));
2889                unlock_ref(lock);
2890                return -1;
2891        }
2892        return 0;
2893}
2894
2895/*
2896 * Commit a change to a loose reference that has already been written
2897 * to the loose reference lockfile. Also update the reflogs if
2898 * necessary, using the specified lockmsg (which can be NULL).
2899 */
2900static int commit_ref_update(struct files_ref_store *refs,
2901                             struct ref_lock *lock,
2902                             const unsigned char *sha1, const char *logmsg,
2903                             struct strbuf *err)
2904{
2905        assert_main_repository(&refs->base, "commit_ref_update");
2906
2907        clear_loose_ref_cache(refs);
2908        if (files_log_ref_write(lock->ref_name, lock->old_oid.hash, sha1,
2909                                logmsg, 0, err)) {
2910                char *old_msg = strbuf_detach(err, NULL);
2911                strbuf_addf(err, "cannot update the ref '%s': %s",
2912                            lock->ref_name, old_msg);
2913                free(old_msg);
2914                unlock_ref(lock);
2915                return -1;
2916        }
2917
2918        if (strcmp(lock->ref_name, "HEAD") != 0) {
2919                /*
2920                 * Special hack: If a branch is updated directly and HEAD
2921                 * points to it (may happen on the remote side of a push
2922                 * for example) then logically the HEAD reflog should be
2923                 * updated too.
2924                 * A generic solution implies reverse symref information,
2925                 * but finding all symrefs pointing to the given branch
2926                 * would be rather costly for this rare event (the direct
2927                 * update of a branch) to be worth it.  So let's cheat and
2928                 * check with HEAD only which should cover 99% of all usage
2929                 * scenarios (even 100% of the default ones).
2930                 */
2931                unsigned char head_sha1[20];
2932                int head_flag;
2933                const char *head_ref;
2934
2935                head_ref = resolve_ref_unsafe("HEAD", RESOLVE_REF_READING,
2936                                              head_sha1, &head_flag);
2937                if (head_ref && (head_flag & REF_ISSYMREF) &&
2938                    !strcmp(head_ref, lock->ref_name)) {
2939                        struct strbuf log_err = STRBUF_INIT;
2940                        if (files_log_ref_write("HEAD", lock->old_oid.hash, sha1,
2941                                          logmsg, 0, &log_err)) {
2942                                error("%s", log_err.buf);
2943                                strbuf_release(&log_err);
2944                        }
2945                }
2946        }
2947
2948        if (commit_ref(lock)) {
2949                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
2950                unlock_ref(lock);
2951                return -1;
2952        }
2953
2954        unlock_ref(lock);
2955        return 0;
2956}
2957
2958static int create_ref_symlink(struct ref_lock *lock, const char *target)
2959{
2960        int ret = -1;
2961#ifndef NO_SYMLINK_HEAD
2962        char *ref_path = get_locked_file_path(lock->lk);
2963        unlink(ref_path);
2964        ret = symlink(target, ref_path);
2965        free(ref_path);
2966
2967        if (ret)
2968                fprintf(stderr, "no symlink - falling back to symbolic ref\n");
2969#endif
2970        return ret;
2971}
2972
2973static void update_symref_reflog(struct ref_lock *lock, const char *refname,
2974                                 const char *target, const char *logmsg)
2975{
2976        struct strbuf err = STRBUF_INIT;
2977        unsigned char new_sha1[20];
2978        if (logmsg && !read_ref(target, new_sha1) &&
2979            files_log_ref_write(refname, lock->old_oid.hash, new_sha1,
2980                                logmsg, 0, &err)) {
2981                error("%s", err.buf);
2982                strbuf_release(&err);
2983        }
2984}
2985
2986static int create_symref_locked(struct ref_lock *lock, const char *refname,
2987                                const char *target, const char *logmsg)
2988{
2989        if (prefer_symlink_refs && !create_ref_symlink(lock, target)) {
2990                update_symref_reflog(lock, refname, target, logmsg);
2991                return 0;
2992        }
2993
2994        if (!fdopen_lock_file(lock->lk, "w"))
2995                return error("unable to fdopen %s: %s",
2996                             lock->lk->tempfile.filename.buf, strerror(errno));
2997
2998        update_symref_reflog(lock, refname, target, logmsg);
2999
3000        /* no error check; commit_ref will check ferror */
3001        fprintf(lock->lk->tempfile.fp, "ref: %s\n", target);
3002        if (commit_ref(lock) < 0)
3003                return error("unable to write symref for %s: %s", refname,
3004                             strerror(errno));
3005        return 0;
3006}
3007
3008static int files_create_symref(struct ref_store *ref_store,
3009                               const char *refname, const char *target,
3010                               const char *logmsg)
3011{
3012        struct files_ref_store *refs =
3013                files_downcast(ref_store, 0, "create_symref");
3014        struct strbuf err = STRBUF_INIT;
3015        struct ref_lock *lock;
3016        int ret;
3017
3018        lock = lock_ref_sha1_basic(refs, refname, NULL,
3019                                   NULL, NULL, REF_NODEREF, NULL,
3020                                   &err);
3021        if (!lock) {
3022                error("%s", err.buf);
3023                strbuf_release(&err);
3024                return -1;
3025        }
3026
3027        ret = create_symref_locked(lock, refname, target, logmsg);
3028        unlock_ref(lock);
3029        return ret;
3030}
3031
3032int set_worktree_head_symref(const char *gitdir, const char *target)
3033{
3034        static struct lock_file head_lock;
3035        struct ref_lock *lock;
3036        struct strbuf head_path = STRBUF_INIT;
3037        const char *head_rel;
3038        int ret;
3039
3040        strbuf_addf(&head_path, "%s/HEAD", absolute_path(gitdir));
3041        if (hold_lock_file_for_update(&head_lock, head_path.buf,
3042                                      LOCK_NO_DEREF) < 0) {
3043                struct strbuf err = STRBUF_INIT;
3044                unable_to_lock_message(head_path.buf, errno, &err);
3045                error("%s", err.buf);
3046                strbuf_release(&err);
3047                strbuf_release(&head_path);
3048                return -1;
3049        }
3050
3051        /* head_rel will be "HEAD" for the main tree, "worktrees/wt/HEAD" for
3052           linked trees */
3053        head_rel = remove_leading_path(head_path.buf,
3054                                       absolute_path(get_git_common_dir()));
3055        /* to make use of create_symref_locked(), initialize ref_lock */
3056        lock = xcalloc(1, sizeof(struct ref_lock));
3057        lock->lk = &head_lock;
3058        lock->ref_name = xstrdup(head_rel);
3059
3060        ret = create_symref_locked(lock, head_rel, target, NULL);
3061
3062        unlock_ref(lock); /* will free lock */
3063        strbuf_release(&head_path);
3064        return ret;
3065}
3066
3067static int files_reflog_exists(struct ref_store *ref_store,
3068                               const char *refname)
3069{
3070        struct stat st;
3071
3072        /* Check validity (but we don't need the result): */
3073        files_downcast(ref_store, 0, "reflog_exists");
3074
3075        return !lstat(git_path("logs/%s", refname), &st) &&
3076                S_ISREG(st.st_mode);
3077}
3078
3079static int files_delete_reflog(struct ref_store *ref_store,
3080                               const char *refname)
3081{
3082        /* Check validity (but we don't need the result): */
3083        files_downcast(ref_store, 0, "delete_reflog");
3084
3085        return remove_path(git_path("logs/%s", refname));
3086}
3087
3088static int show_one_reflog_ent(struct strbuf *sb, each_reflog_ent_fn fn, void *cb_data)
3089{
3090        unsigned char osha1[20], nsha1[20];
3091        char *email_end, *message;
3092        unsigned long timestamp;
3093        int tz;
3094
3095        /* old SP new SP name <email> SP time TAB msg LF */
3096        if (sb->len < 83 || sb->buf[sb->len - 1] != '\n' ||
3097            get_sha1_hex(sb->buf, osha1) || sb->buf[40] != ' ' ||
3098            get_sha1_hex(sb->buf + 41, nsha1) || sb->buf[81] != ' ' ||
3099            !(email_end = strchr(sb->buf + 82, '>')) ||
3100            email_end[1] != ' ' ||
3101            !(timestamp = strtoul(email_end + 2, &message, 10)) ||
3102            !message || message[0] != ' ' ||
3103            (message[1] != '+' && message[1] != '-') ||
3104            !isdigit(message[2]) || !isdigit(message[3]) ||
3105            !isdigit(message[4]) || !isdigit(message[5]))
3106                return 0; /* corrupt? */
3107        email_end[1] = '\0';
3108        tz = strtol(message + 1, NULL, 10);
3109        if (message[6] != '\t')
3110                message += 6;
3111        else
3112                message += 7;
3113        return fn(osha1, nsha1, sb->buf + 82, timestamp, tz, message, cb_data);
3114}
3115
3116static char *find_beginning_of_line(char *bob, char *scan)
3117{
3118        while (bob < scan && *(--scan) != '\n')
3119                ; /* keep scanning backwards */
3120        /*
3121         * Return either beginning of the buffer, or LF at the end of
3122         * the previous line.
3123         */
3124        return scan;
3125}
3126
3127static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
3128                                             const char *refname,
3129                                             each_reflog_ent_fn fn,
3130                                             void *cb_data)
3131{
3132        struct strbuf sb = STRBUF_INIT;
3133        FILE *logfp;
3134        long pos;
3135        int ret = 0, at_tail = 1;
3136
3137        /* Check validity (but we don't need the result): */
3138        files_downcast(ref_store, 0, "for_each_reflog_ent_reverse");
3139
3140        logfp = fopen(git_path("logs/%s", refname), "r");
3141        if (!logfp)
3142                return -1;
3143
3144        /* Jump to the end */
3145        if (fseek(logfp, 0, SEEK_END) < 0)
3146                return error("cannot seek back reflog for %s: %s",
3147                             refname, strerror(errno));
3148        pos = ftell(logfp);
3149        while (!ret && 0 < pos) {
3150                int cnt;
3151                size_t nread;
3152                char buf[BUFSIZ];
3153                char *endp, *scanp;
3154
3155                /* Fill next block from the end */
3156                cnt = (sizeof(buf) < pos) ? sizeof(buf) : pos;
3157                if (fseek(logfp, pos - cnt, SEEK_SET))
3158                        return error("cannot seek back reflog for %s: %s",
3159                                     refname, strerror(errno));
3160                nread = fread(buf, cnt, 1, logfp);
3161                if (nread != 1)
3162                        return error("cannot read %d bytes from reflog for %s: %s",
3163                                     cnt, refname, strerror(errno));
3164                pos -= cnt;
3165
3166                scanp = endp = buf + cnt;
3167                if (at_tail && scanp[-1] == '\n')
3168                        /* Looking at the final LF at the end of the file */
3169                        scanp--;
3170                at_tail = 0;
3171
3172                while (buf < scanp) {
3173                        /*
3174                         * terminating LF of the previous line, or the beginning
3175                         * of the buffer.
3176                         */
3177                        char *bp;
3178
3179                        bp = find_beginning_of_line(buf, scanp);
3180
3181                        if (*bp == '\n') {
3182                                /*
3183                                 * The newline is the end of the previous line,
3184                                 * so we know we have complete line starting
3185                                 * at (bp + 1). Prefix it onto any prior data
3186                                 * we collected for the line and process it.
3187                                 */
3188                                strbuf_splice(&sb, 0, 0, bp + 1, endp - (bp + 1));
3189                                scanp = bp;
3190                                endp = bp + 1;
3191                                ret = show_one_reflog_ent(&sb, fn, cb_data);
3192                                strbuf_reset(&sb);
3193                                if (ret)
3194                                        break;
3195                        } else if (!pos) {
3196                                /*
3197                                 * We are at the start of the buffer, and the
3198                                 * start of the file; there is no previous
3199                                 * line, and we have everything for this one.
3200                                 * Process it, and we can end the loop.
3201                                 */
3202                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
3203                                ret = show_one_reflog_ent(&sb, fn, cb_data);
3204                                strbuf_reset(&sb);
3205                                break;
3206                        }
3207
3208                        if (bp == buf) {
3209                                /*
3210                                 * We are at the start of the buffer, and there
3211                                 * is more file to read backwards. Which means
3212                                 * we are in the middle of a line. Note that we
3213                                 * may get here even if *bp was a newline; that
3214                                 * just means we are at the exact end of the
3215                                 * previous line, rather than some spot in the
3216                                 * middle.
3217                                 *
3218                                 * Save away what we have to be combined with
3219                                 * the data from the next read.
3220                                 */
3221                                strbuf_splice(&sb, 0, 0, buf, endp - buf);
3222                                break;
3223                        }
3224                }
3225
3226        }
3227        if (!ret && sb.len)
3228                die("BUG: reverse reflog parser had leftover data");
3229
3230        fclose(logfp);
3231        strbuf_release(&sb);
3232        return ret;
3233}
3234
3235static int files_for_each_reflog_ent(struct ref_store *ref_store,
3236                                     const char *refname,
3237                                     each_reflog_ent_fn fn, void *cb_data)
3238{
3239        FILE *logfp;
3240        struct strbuf sb = STRBUF_INIT;
3241        int ret = 0;
3242
3243        /* Check validity (but we don't need the result): */
3244        files_downcast(ref_store, 0, "for_each_reflog_ent");
3245
3246        logfp = fopen(git_path("logs/%s", refname), "r");
3247        if (!logfp)
3248                return -1;
3249
3250        while (!ret && !strbuf_getwholeline(&sb, logfp, '\n'))
3251                ret = show_one_reflog_ent(&sb, fn, cb_data);
3252        fclose(logfp);
3253        strbuf_release(&sb);
3254        return ret;
3255}
3256
3257struct files_reflog_iterator {
3258        struct ref_iterator base;
3259
3260        struct dir_iterator *dir_iterator;
3261        struct object_id oid;
3262};
3263
3264static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
3265{
3266        struct files_reflog_iterator *iter =
3267                (struct files_reflog_iterator *)ref_iterator;
3268        struct dir_iterator *diter = iter->dir_iterator;
3269        int ok;
3270
3271        while ((ok = dir_iterator_advance(diter)) == ITER_OK) {
3272                int flags;
3273
3274                if (!S_ISREG(diter->st.st_mode))
3275                        continue;
3276                if (diter->basename[0] == '.')
3277                        continue;
3278                if (ends_with(diter->basename, ".lock"))
3279                        continue;
3280
3281                if (read_ref_full(diter->relative_path, 0,
3282                                  iter->oid.hash, &flags)) {
3283                        error("bad ref for %s", diter->path.buf);
3284                        continue;
3285                }
3286
3287                iter->base.refname = diter->relative_path;
3288                iter->base.oid = &iter->oid;
3289                iter->base.flags = flags;
3290                return ITER_OK;
3291        }
3292
3293        iter->dir_iterator = NULL;
3294        if (ref_iterator_abort(ref_iterator) == ITER_ERROR)
3295                ok = ITER_ERROR;
3296        return ok;
3297}
3298
3299static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
3300                                   struct object_id *peeled)
3301{
3302        die("BUG: ref_iterator_peel() called for reflog_iterator");
3303}
3304
3305static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
3306{
3307        struct files_reflog_iterator *iter =
3308                (struct files_reflog_iterator *)ref_iterator;
3309        int ok = ITER_DONE;
3310
3311        if (iter->dir_iterator)
3312                ok = dir_iterator_abort(iter->dir_iterator);
3313
3314        base_ref_iterator_free(ref_iterator);
3315        return ok;
3316}
3317
3318static struct ref_iterator_vtable files_reflog_iterator_vtable = {
3319        files_reflog_iterator_advance,
3320        files_reflog_iterator_peel,
3321        files_reflog_iterator_abort
3322};
3323
3324static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
3325{
3326        struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
3327        struct ref_iterator *ref_iterator = &iter->base;
3328
3329        /* Check validity (but we don't need the result): */
3330        files_downcast(ref_store, 0, "reflog_iterator_begin");
3331
3332        base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
3333        iter->dir_iterator = dir_iterator_begin(git_path("logs"));
3334        return ref_iterator;
3335}
3336
3337static int ref_update_reject_duplicates(struct string_list *refnames,
3338                                        struct strbuf *err)
3339{
3340        int i, n = refnames->nr;
3341
3342        assert(err);
3343
3344        for (i = 1; i < n; i++)
3345                if (!strcmp(refnames->items[i - 1].string, refnames->items[i].string)) {
3346                        strbuf_addf(err,
3347                                    "multiple updates for ref '%s' not allowed.",
3348                                    refnames->items[i].string);
3349                        return 1;
3350                }
3351        return 0;
3352}
3353
3354/*
3355 * If update is a direct update of head_ref (the reference pointed to
3356 * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
3357 */
3358static int split_head_update(struct ref_update *update,
3359                             struct ref_transaction *transaction,
3360                             const char *head_ref,
3361                             struct string_list *affected_refnames,
3362                             struct strbuf *err)
3363{
3364        struct string_list_item *item;
3365        struct ref_update *new_update;
3366
3367        if ((update->flags & REF_LOG_ONLY) ||
3368            (update->flags & REF_ISPRUNING) ||
3369            (update->flags & REF_UPDATE_VIA_HEAD))
3370                return 0;
3371
3372        if (strcmp(update->refname, head_ref))
3373                return 0;
3374
3375        /*
3376         * First make sure that HEAD is not already in the
3377         * transaction. This insertion is O(N) in the transaction
3378         * size, but it happens at most once per transaction.
3379         */
3380        item = string_list_insert(affected_refnames, "HEAD");
3381        if (item->util) {
3382                /* An entry already existed */
3383                strbuf_addf(err,
3384                            "multiple updates for 'HEAD' (including one "
3385                            "via its referent '%s') are not allowed",
3386                            update->refname);
3387                return TRANSACTION_NAME_CONFLICT;
3388        }
3389
3390        new_update = ref_transaction_add_update(
3391                        transaction, "HEAD",
3392                        update->flags | REF_LOG_ONLY | REF_NODEREF,
3393                        update->new_sha1, update->old_sha1,
3394                        update->msg);
3395
3396        item->util = new_update;
3397
3398        return 0;
3399}
3400
3401/*
3402 * update is for a symref that points at referent and doesn't have
3403 * REF_NODEREF set. Split it into two updates:
3404 * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
3405 * - A new, separate update for the referent reference
3406 * Note that the new update will itself be subject to splitting when
3407 * the iteration gets to it.
3408 */
3409static int split_symref_update(struct files_ref_store *refs,
3410                               struct ref_update *update,
3411                               const char *referent,
3412                               struct ref_transaction *transaction,
3413                               struct string_list *affected_refnames,
3414                               struct strbuf *err)
3415{
3416        struct string_list_item *item;
3417        struct ref_update *new_update;
3418        unsigned int new_flags;
3419
3420        /*
3421         * First make sure that referent is not already in the
3422         * transaction. This insertion is O(N) in the transaction
3423         * size, but it happens at most once per symref in a
3424         * transaction.
3425         */
3426        item = string_list_insert(affected_refnames, referent);
3427        if (item->util) {
3428                /* An entry already existed */
3429                strbuf_addf(err,
3430                            "multiple updates for '%s' (including one "
3431                            "via symref '%s') are not allowed",
3432                            referent, update->refname);
3433                return TRANSACTION_NAME_CONFLICT;
3434        }
3435
3436        new_flags = update->flags;
3437        if (!strcmp(update->refname, "HEAD")) {
3438                /*
3439                 * Record that the new update came via HEAD, so that
3440                 * when we process it, split_head_update() doesn't try
3441                 * to add another reflog update for HEAD. Note that
3442                 * this bit will be propagated if the new_update
3443                 * itself needs to be split.
3444                 */
3445                new_flags |= REF_UPDATE_VIA_HEAD;
3446        }
3447
3448        new_update = ref_transaction_add_update(
3449                        transaction, referent, new_flags,
3450                        update->new_sha1, update->old_sha1,
3451                        update->msg);
3452
3453        new_update->parent_update = update;
3454
3455        /*
3456         * Change the symbolic ref update to log only. Also, it
3457         * doesn't need to check its old SHA-1 value, as that will be
3458         * done when new_update is processed.
3459         */
3460        update->flags |= REF_LOG_ONLY | REF_NODEREF;
3461        update->flags &= ~REF_HAVE_OLD;
3462
3463        item->util = new_update;
3464
3465        return 0;
3466}
3467
3468/*
3469 * Return the refname under which update was originally requested.
3470 */
3471static const char *original_update_refname(struct ref_update *update)
3472{
3473        while (update->parent_update)
3474                update = update->parent_update;
3475
3476        return update->refname;
3477}
3478
3479/*
3480 * Check whether the REF_HAVE_OLD and old_oid values stored in update
3481 * are consistent with oid, which is the reference's current value. If
3482 * everything is OK, return 0; otherwise, write an error message to
3483 * err and return -1.
3484 */
3485static int check_old_oid(struct ref_update *update, struct object_id *oid,
3486                         struct strbuf *err)
3487{
3488        if (!(update->flags & REF_HAVE_OLD) ||
3489                   !hashcmp(oid->hash, update->old_sha1))
3490                return 0;
3491
3492        if (is_null_sha1(update->old_sha1))
3493                strbuf_addf(err, "cannot lock ref '%s': "
3494                            "reference already exists",
3495                            original_update_refname(update));
3496        else if (is_null_oid(oid))
3497                strbuf_addf(err, "cannot lock ref '%s': "
3498                            "reference is missing but expected %s",
3499                            original_update_refname(update),
3500                            sha1_to_hex(update->old_sha1));
3501        else
3502                strbuf_addf(err, "cannot lock ref '%s': "
3503                            "is at %s but expected %s",
3504                            original_update_refname(update),
3505                            oid_to_hex(oid),
3506                            sha1_to_hex(update->old_sha1));
3507
3508        return -1;
3509}
3510
3511/*
3512 * Prepare for carrying out update:
3513 * - Lock the reference referred to by update.
3514 * - Read the reference under lock.
3515 * - Check that its old SHA-1 value (if specified) is correct, and in
3516 *   any case record it in update->lock->old_oid for later use when
3517 *   writing the reflog.
3518 * - If it is a symref update without REF_NODEREF, split it up into a
3519 *   REF_LOG_ONLY update of the symref and add a separate update for
3520 *   the referent to transaction.
3521 * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
3522 *   update of HEAD.
3523 */
3524static int lock_ref_for_update(struct files_ref_store *refs,
3525                               struct ref_update *update,
3526                               struct ref_transaction *transaction,
3527                               const char *head_ref,
3528                               struct string_list *affected_refnames,
3529                               struct strbuf *err)
3530{
3531        struct strbuf referent = STRBUF_INIT;
3532        int mustexist = (update->flags & REF_HAVE_OLD) &&
3533                !is_null_sha1(update->old_sha1);
3534        int ret;
3535        struct ref_lock *lock;
3536
3537        assert_main_repository(&refs->base, "lock_ref_for_update");
3538
3539        if ((update->flags & REF_HAVE_NEW) && is_null_sha1(update->new_sha1))
3540                update->flags |= REF_DELETING;
3541
3542        if (head_ref) {
3543                ret = split_head_update(update, transaction, head_ref,
3544                                        affected_refnames, err);
3545                if (ret)
3546                        return ret;
3547        }
3548
3549        ret = lock_raw_ref(refs, update->refname, mustexist,
3550                           affected_refnames, NULL,
3551                           &lock, &referent,
3552                           &update->type, err);
3553        if (ret) {
3554                char *reason;
3555
3556                reason = strbuf_detach(err, NULL);
3557                strbuf_addf(err, "cannot lock ref '%s': %s",
3558                            original_update_refname(update), reason);
3559                free(reason);
3560                return ret;
3561        }
3562
3563        update->backend_data = lock;
3564
3565        if (update->type & REF_ISSYMREF) {
3566                if (update->flags & REF_NODEREF) {
3567                        /*
3568                         * We won't be reading the referent as part of
3569                         * the transaction, so we have to read it here
3570                         * to record and possibly check old_sha1:
3571                         */
3572                        if (read_ref_full(referent.buf, 0,
3573                                          lock->old_oid.hash, NULL)) {
3574                                if (update->flags & REF_HAVE_OLD) {
3575                                        strbuf_addf(err, "cannot lock ref '%s': "
3576                                                    "error reading reference",
3577                                                    original_update_refname(update));
3578                                        return -1;
3579                                }
3580                        } else if (check_old_oid(update, &lock->old_oid, err)) {
3581                                return TRANSACTION_GENERIC_ERROR;
3582                        }
3583                } else {
3584                        /*
3585                         * Create a new update for the reference this
3586                         * symref is pointing at. Also, we will record
3587                         * and verify old_sha1 for this update as part
3588                         * of processing the split-off update, so we
3589                         * don't have to do it here.
3590                         */
3591                        ret = split_symref_update(refs, update,
3592                                                  referent.buf, transaction,
3593                                                  affected_refnames, err);
3594                        if (ret)
3595                                return ret;
3596                }
3597        } else {
3598                struct ref_update *parent_update;
3599
3600                if (check_old_oid(update, &lock->old_oid, err))
3601                        return TRANSACTION_GENERIC_ERROR;
3602
3603                /*
3604                 * If this update is happening indirectly because of a
3605                 * symref update, record the old SHA-1 in the parent
3606                 * update:
3607                 */
3608                for (parent_update = update->parent_update;
3609                     parent_update;
3610                     parent_update = parent_update->parent_update) {
3611                        struct ref_lock *parent_lock = parent_update->backend_data;
3612                        oidcpy(&parent_lock->old_oid, &lock->old_oid);
3613                }
3614        }
3615
3616        if ((update->flags & REF_HAVE_NEW) &&
3617            !(update->flags & REF_DELETING) &&
3618            !(update->flags & REF_LOG_ONLY)) {
3619                if (!(update->type & REF_ISSYMREF) &&
3620                    !hashcmp(lock->old_oid.hash, update->new_sha1)) {
3621                        /*
3622                         * The reference already has the desired
3623                         * value, so we don't need to write it.
3624                         */
3625                } else if (write_ref_to_lockfile(lock, update->new_sha1,
3626                                                 err)) {
3627                        char *write_err = strbuf_detach(err, NULL);
3628
3629                        /*
3630                         * The lock was freed upon failure of
3631                         * write_ref_to_lockfile():
3632                         */
3633                        update->backend_data = NULL;
3634                        strbuf_addf(err,
3635                                    "cannot update ref '%s': %s",
3636                                    update->refname, write_err);
3637                        free(write_err);
3638                        return TRANSACTION_GENERIC_ERROR;
3639                } else {
3640                        update->flags |= REF_NEEDS_COMMIT;
3641                }
3642        }
3643        if (!(update->flags & REF_NEEDS_COMMIT)) {
3644                /*
3645                 * We didn't call write_ref_to_lockfile(), so
3646                 * the lockfile is still open. Close it to
3647                 * free up the file descriptor:
3648                 */
3649                if (close_ref(lock)) {
3650                        strbuf_addf(err, "couldn't close '%s.lock'",
3651                                    update->refname);
3652                        return TRANSACTION_GENERIC_ERROR;
3653                }
3654        }
3655        return 0;
3656}
3657
3658static int files_transaction_commit(struct ref_store *ref_store,
3659                                    struct ref_transaction *transaction,
3660                                    struct strbuf *err)
3661{
3662        struct files_ref_store *refs =
3663                files_downcast(ref_store, 0, "ref_transaction_commit");
3664        int ret = 0, i;
3665        struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
3666        struct string_list_item *ref_to_delete;
3667        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
3668        char *head_ref = NULL;
3669        int head_type;
3670        struct object_id head_oid;
3671
3672        assert(err);
3673
3674        if (transaction->state != REF_TRANSACTION_OPEN)
3675                die("BUG: commit called for transaction that is not open");
3676
3677        if (!transaction->nr) {
3678                transaction->state = REF_TRANSACTION_CLOSED;
3679                return 0;
3680        }
3681
3682        /*
3683         * Fail if a refname appears more than once in the
3684         * transaction. (If we end up splitting up any updates using
3685         * split_symref_update() or split_head_update(), those
3686         * functions will check that the new updates don't have the
3687         * same refname as any existing ones.)
3688         */
3689        for (i = 0; i < transaction->nr; i++) {
3690                struct ref_update *update = transaction->updates[i];
3691                struct string_list_item *item =
3692                        string_list_append(&affected_refnames, update->refname);
3693
3694                /*
3695                 * We store a pointer to update in item->util, but at
3696                 * the moment we never use the value of this field
3697                 * except to check whether it is non-NULL.
3698                 */
3699                item->util = update;
3700        }
3701        string_list_sort(&affected_refnames);
3702        if (ref_update_reject_duplicates(&affected_refnames, err)) {
3703                ret = TRANSACTION_GENERIC_ERROR;
3704                goto cleanup;
3705        }
3706
3707        /*
3708         * Special hack: If a branch is updated directly and HEAD
3709         * points to it (may happen on the remote side of a push
3710         * for example) then logically the HEAD reflog should be
3711         * updated too.
3712         *
3713         * A generic solution would require reverse symref lookups,
3714         * but finding all symrefs pointing to a given branch would be
3715         * rather costly for this rare event (the direct update of a
3716         * branch) to be worth it. So let's cheat and check with HEAD
3717         * only, which should cover 99% of all usage scenarios (even
3718         * 100% of the default ones).
3719         *
3720         * So if HEAD is a symbolic reference, then record the name of
3721         * the reference that it points to. If we see an update of
3722         * head_ref within the transaction, then split_head_update()
3723         * arranges for the reflog of HEAD to be updated, too.
3724         */
3725        head_ref = resolve_refdup("HEAD", RESOLVE_REF_NO_RECURSE,
3726                                  head_oid.hash, &head_type);
3727
3728        if (head_ref && !(head_type & REF_ISSYMREF)) {
3729                free(head_ref);
3730                head_ref = NULL;
3731        }
3732
3733        /*
3734         * Acquire all locks, verify old values if provided, check
3735         * that new values are valid, and write new values to the
3736         * lockfiles, ready to be activated. Only keep one lockfile
3737         * open at a time to avoid running out of file descriptors.
3738         */
3739        for (i = 0; i < transaction->nr; i++) {
3740                struct ref_update *update = transaction->updates[i];
3741
3742                ret = lock_ref_for_update(refs, update, transaction,
3743                                          head_ref, &affected_refnames, err);
3744                if (ret)
3745                        goto cleanup;
3746        }
3747
3748        /* Perform updates first so live commits remain referenced */
3749        for (i = 0; i < transaction->nr; i++) {
3750                struct ref_update *update = transaction->updates[i];
3751                struct ref_lock *lock = update->backend_data;
3752
3753                if (update->flags & REF_NEEDS_COMMIT ||
3754                    update->flags & REF_LOG_ONLY) {
3755                        if (files_log_ref_write(lock->ref_name,
3756                                                lock->old_oid.hash,
3757                                                update->new_sha1,
3758                                                update->msg, update->flags,
3759                                                err)) {
3760                                char *old_msg = strbuf_detach(err, NULL);
3761
3762                                strbuf_addf(err, "cannot update the ref '%s': %s",
3763                                            lock->ref_name, old_msg);
3764                                free(old_msg);
3765                                unlock_ref(lock);
3766                                update->backend_data = NULL;
3767                                ret = TRANSACTION_GENERIC_ERROR;
3768                                goto cleanup;
3769                        }
3770                }
3771                if (update->flags & REF_NEEDS_COMMIT) {
3772                        clear_loose_ref_cache(refs);
3773                        if (commit_ref(lock)) {
3774                                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
3775                                unlock_ref(lock);
3776                                update->backend_data = NULL;
3777                                ret = TRANSACTION_GENERIC_ERROR;
3778                                goto cleanup;
3779                        }
3780                }
3781        }
3782        /* Perform deletes now that updates are safely completed */
3783        for (i = 0; i < transaction->nr; i++) {
3784                struct ref_update *update = transaction->updates[i];
3785                struct ref_lock *lock = update->backend_data;
3786
3787                if (update->flags & REF_DELETING &&
3788                    !(update->flags & REF_LOG_ONLY)) {
3789                        if (!(update->type & REF_ISPACKED) ||
3790                            update->type & REF_ISSYMREF) {
3791                                /* It is a loose reference. */
3792                                if (unlink_or_msg(git_path("%s", lock->ref_name), err)) {
3793                                        ret = TRANSACTION_GENERIC_ERROR;
3794                                        goto cleanup;
3795                                }
3796                                update->flags |= REF_DELETED_LOOSE;
3797                        }
3798
3799                        if (!(update->flags & REF_ISPRUNING))
3800                                string_list_append(&refs_to_delete,
3801                                                   lock->ref_name);
3802                }
3803        }
3804
3805        if (repack_without_refs(refs, &refs_to_delete, err)) {
3806                ret = TRANSACTION_GENERIC_ERROR;
3807                goto cleanup;
3808        }
3809
3810        /* Delete the reflogs of any references that were deleted: */
3811        for_each_string_list_item(ref_to_delete, &refs_to_delete) {
3812                if (!unlink_or_warn(git_path("logs/%s", ref_to_delete->string)))
3813                        try_remove_empty_parents(ref_to_delete->string,
3814                                                 REMOVE_EMPTY_PARENTS_REFLOG);
3815        }
3816
3817        clear_loose_ref_cache(refs);
3818
3819cleanup:
3820        transaction->state = REF_TRANSACTION_CLOSED;
3821
3822        for (i = 0; i < transaction->nr; i++) {
3823                struct ref_update *update = transaction->updates[i];
3824                struct ref_lock *lock = update->backend_data;
3825
3826                if (lock)
3827                        unlock_ref(lock);
3828
3829                if (update->flags & REF_DELETED_LOOSE) {
3830                        /*
3831                         * The loose reference was deleted. Delete any
3832                         * empty parent directories. (Note that this
3833                         * can only work because we have already
3834                         * removed the lockfile.)
3835                         */
3836                        try_remove_empty_parents(update->refname,
3837                                                 REMOVE_EMPTY_PARENTS_REF);
3838                }
3839        }
3840
3841        string_list_clear(&refs_to_delete, 0);
3842        free(head_ref);
3843        string_list_clear(&affected_refnames, 0);
3844
3845        return ret;
3846}
3847
3848static int ref_present(const char *refname,
3849                       const struct object_id *oid, int flags, void *cb_data)
3850{
3851        struct string_list *affected_refnames = cb_data;
3852
3853        return string_list_has_string(affected_refnames, refname);
3854}
3855
3856static int files_initial_transaction_commit(struct ref_store *ref_store,
3857                                            struct ref_transaction *transaction,
3858                                            struct strbuf *err)
3859{
3860        struct files_ref_store *refs =
3861                files_downcast(ref_store, 0, "initial_ref_transaction_commit");
3862        int ret = 0, i;
3863        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
3864
3865        assert(err);
3866
3867        if (transaction->state != REF_TRANSACTION_OPEN)
3868                die("BUG: commit called for transaction that is not open");
3869
3870        /* Fail if a refname appears more than once in the transaction: */
3871        for (i = 0; i < transaction->nr; i++)
3872                string_list_append(&affected_refnames,
3873                                   transaction->updates[i]->refname);
3874        string_list_sort(&affected_refnames);
3875        if (ref_update_reject_duplicates(&affected_refnames, err)) {
3876                ret = TRANSACTION_GENERIC_ERROR;
3877                goto cleanup;
3878        }
3879
3880        /*
3881         * It's really undefined to call this function in an active
3882         * repository or when there are existing references: we are
3883         * only locking and changing packed-refs, so (1) any
3884         * simultaneous processes might try to change a reference at
3885         * the same time we do, and (2) any existing loose versions of
3886         * the references that we are setting would have precedence
3887         * over our values. But some remote helpers create the remote
3888         * "HEAD" and "master" branches before calling this function,
3889         * so here we really only check that none of the references
3890         * that we are creating already exists.
3891         */
3892        if (for_each_rawref(ref_present, &affected_refnames))
3893                die("BUG: initial ref transaction called with existing refs");
3894
3895        for (i = 0; i < transaction->nr; i++) {
3896                struct ref_update *update = transaction->updates[i];
3897
3898                if ((update->flags & REF_HAVE_OLD) &&
3899                    !is_null_sha1(update->old_sha1))
3900                        die("BUG: initial ref transaction with old_sha1 set");
3901                if (verify_refname_available(update->refname,
3902                                             &affected_refnames, NULL,
3903                                             err)) {
3904                        ret = TRANSACTION_NAME_CONFLICT;
3905                        goto cleanup;
3906                }
3907        }
3908
3909        if (lock_packed_refs(refs, 0)) {
3910                strbuf_addf(err, "unable to lock packed-refs file: %s",
3911                            strerror(errno));
3912                ret = TRANSACTION_GENERIC_ERROR;
3913                goto cleanup;
3914        }
3915
3916        for (i = 0; i < transaction->nr; i++) {
3917                struct ref_update *update = transaction->updates[i];
3918
3919                if ((update->flags & REF_HAVE_NEW) &&
3920                    !is_null_sha1(update->new_sha1))
3921                        add_packed_ref(refs, update->refname, update->new_sha1);
3922        }
3923
3924        if (commit_packed_refs(refs)) {
3925                strbuf_addf(err, "unable to commit packed-refs file: %s",
3926                            strerror(errno));
3927                ret = TRANSACTION_GENERIC_ERROR;
3928                goto cleanup;
3929        }
3930
3931cleanup:
3932        transaction->state = REF_TRANSACTION_CLOSED;
3933        string_list_clear(&affected_refnames, 0);
3934        return ret;
3935}
3936
3937struct expire_reflog_cb {
3938        unsigned int flags;
3939        reflog_expiry_should_prune_fn *should_prune_fn;
3940        void *policy_cb;
3941        FILE *newlog;
3942        unsigned char last_kept_sha1[20];
3943};
3944
3945static int expire_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
3946                             const char *email, unsigned long timestamp, int tz,
3947                             const char *message, void *cb_data)
3948{
3949        struct expire_reflog_cb *cb = cb_data;
3950        struct expire_reflog_policy_cb *policy_cb = cb->policy_cb;
3951
3952        if (cb->flags & EXPIRE_REFLOGS_REWRITE)
3953                osha1 = cb->last_kept_sha1;
3954
3955        if ((*cb->should_prune_fn)(osha1, nsha1, email, timestamp, tz,
3956                                   message, policy_cb)) {
3957                if (!cb->newlog)
3958                        printf("would prune %s", message);
3959                else if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3960                        printf("prune %s", message);
3961        } else {
3962                if (cb->newlog) {
3963                        fprintf(cb->newlog, "%s %s %s %lu %+05d\t%s",
3964                                sha1_to_hex(osha1), sha1_to_hex(nsha1),
3965                                email, timestamp, tz, message);
3966                        hashcpy(cb->last_kept_sha1, nsha1);
3967                }
3968                if (cb->flags & EXPIRE_REFLOGS_VERBOSE)
3969                        printf("keep %s", message);
3970        }
3971        return 0;
3972}
3973
3974static int files_reflog_expire(struct ref_store *ref_store,
3975                               const char *refname, const unsigned char *sha1,
3976                               unsigned int flags,
3977                               reflog_expiry_prepare_fn prepare_fn,
3978                               reflog_expiry_should_prune_fn should_prune_fn,
3979                               reflog_expiry_cleanup_fn cleanup_fn,
3980                               void *policy_cb_data)
3981{
3982        struct files_ref_store *refs =
3983                files_downcast(ref_store, 0, "reflog_expire");
3984        static struct lock_file reflog_lock;
3985        struct expire_reflog_cb cb;
3986        struct ref_lock *lock;
3987        char *log_file;
3988        int status = 0;
3989        int type;
3990        struct strbuf err = STRBUF_INIT;
3991
3992        memset(&cb, 0, sizeof(cb));
3993        cb.flags = flags;
3994        cb.policy_cb = policy_cb_data;
3995        cb.should_prune_fn = should_prune_fn;
3996
3997        /*
3998         * The reflog file is locked by holding the lock on the
3999         * reference itself, plus we might need to update the
4000         * reference if --updateref was specified:
4001         */
4002        lock = lock_ref_sha1_basic(refs, refname, sha1,
4003                                   NULL, NULL, REF_NODEREF,
4004                                   &type, &err);
4005        if (!lock) {
4006                error("cannot lock ref '%s': %s", refname, err.buf);
4007                strbuf_release(&err);
4008                return -1;
4009        }
4010        if (!reflog_exists(refname)) {
4011                unlock_ref(lock);
4012                return 0;
4013        }
4014
4015        log_file = git_pathdup("logs/%s", refname);
4016        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
4017                /*
4018                 * Even though holding $GIT_DIR/logs/$reflog.lock has
4019                 * no locking implications, we use the lock_file
4020                 * machinery here anyway because it does a lot of the
4021                 * work we need, including cleaning up if the program
4022                 * exits unexpectedly.
4023                 */
4024                if (hold_lock_file_for_update(&reflog_lock, log_file, 0) < 0) {
4025                        struct strbuf err = STRBUF_INIT;
4026                        unable_to_lock_message(log_file, errno, &err);
4027                        error("%s", err.buf);
4028                        strbuf_release(&err);
4029                        goto failure;
4030                }
4031                cb.newlog = fdopen_lock_file(&reflog_lock, "w");
4032                if (!cb.newlog) {
4033                        error("cannot fdopen %s (%s)",
4034                              get_lock_file_path(&reflog_lock), strerror(errno));
4035                        goto failure;
4036                }
4037        }
4038
4039        (*prepare_fn)(refname, sha1, cb.policy_cb);
4040        for_each_reflog_ent(refname, expire_reflog_ent, &cb);
4041        (*cleanup_fn)(cb.policy_cb);
4042
4043        if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
4044                /*
4045                 * It doesn't make sense to adjust a reference pointed
4046                 * to by a symbolic ref based on expiring entries in
4047                 * the symbolic reference's reflog. Nor can we update
4048                 * a reference if there are no remaining reflog
4049                 * entries.
4050                 */
4051                int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
4052                        !(type & REF_ISSYMREF) &&
4053                        !is_null_sha1(cb.last_kept_sha1);
4054
4055                if (close_lock_file(&reflog_lock)) {
4056                        status |= error("couldn't write %s: %s", log_file,
4057                                        strerror(errno));
4058                } else if (update &&
4059                           (write_in_full(get_lock_file_fd(lock->lk),
4060                                sha1_to_hex(cb.last_kept_sha1), 40) != 40 ||
4061                            write_str_in_full(get_lock_file_fd(lock->lk), "\n") != 1 ||
4062                            close_ref(lock) < 0)) {
4063                        status |= error("couldn't write %s",
4064                                        get_lock_file_path(lock->lk));
4065                        rollback_lock_file(&reflog_lock);
4066                } else if (commit_lock_file(&reflog_lock)) {
4067                        status |= error("unable to write reflog '%s' (%s)",
4068                                        log_file, strerror(errno));
4069                } else if (update && commit_ref(lock)) {
4070                        status |= error("couldn't set %s", lock->ref_name);
4071                }
4072        }
4073        free(log_file);
4074        unlock_ref(lock);
4075        return status;
4076
4077 failure:
4078        rollback_lock_file(&reflog_lock);
4079        free(log_file);
4080        unlock_ref(lock);
4081        return -1;
4082}
4083
4084static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
4085{
4086        /* Check validity (but we don't need the result): */
4087        files_downcast(ref_store, 0, "init_db");
4088
4089        /*
4090         * Create .git/refs/{heads,tags}
4091         */
4092        safe_create_dir(git_path("refs/heads"), 1);
4093        safe_create_dir(git_path("refs/tags"), 1);
4094        if (get_shared_repository()) {
4095                adjust_shared_perm(git_path("refs/heads"));
4096                adjust_shared_perm(git_path("refs/tags"));
4097        }
4098        return 0;
4099}
4100
4101struct ref_storage_be refs_be_files = {
4102        NULL,
4103        "files",
4104        files_ref_store_create,
4105        files_init_db,
4106        files_transaction_commit,
4107        files_initial_transaction_commit,
4108
4109        files_pack_refs,
4110        files_peel_ref,
4111        files_create_symref,
4112        files_delete_refs,
4113        files_rename_ref,
4114
4115        files_ref_iterator_begin,
4116        files_read_raw_ref,
4117        files_verify_refname_available,
4118
4119        files_reflog_iterator_begin,
4120        files_for_each_reflog_ent,
4121        files_for_each_reflog_ent_reverse,
4122        files_reflog_exists,
4123        files_create_reflog,
4124        files_delete_reflog,
4125        files_reflog_expire
4126};