try_remove_empty_parents(): don't trash argument contents
[gitweb.git] / refs / files-backend.c
index 2455564352e1dafd5a95cd25b7279ead69b24660..88f8c7aa4b2be898712f90be4394e6233dee9f80 100644 (file)
@@ -39,7 +39,7 @@ struct ref_value {
        struct object_id peeled;
 };
 
-struct ref_cache;
+struct files_ref_store;
 
 /*
  * Information used (along with the information in ref_entry) to
@@ -78,8 +78,8 @@ struct ref_dir {
         */
        int sorted;
 
-       /* A pointer to the ref_cache that contains this ref_dir. */
-       struct ref_cache *ref_cache;
+       /* A pointer to the files_ref_store that contains this ref_dir. */
+       struct files_ref_store *ref_store;
 
        struct ref_entry **entries;
 };
@@ -161,7 +161,7 @@ struct ref_entry {
 
 static void read_loose_refs(const char *dirname, struct ref_dir *dir);
 static int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len);
-static struct ref_entry *create_dir_entry(struct ref_cache *ref_cache,
+static struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
                                          const char *dirname, size_t len,
                                          int incomplete);
 static void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry);
@@ -183,7 +183,7 @@ static struct ref_dir *get_ref_dir(struct ref_entry *entry)
                        int pos = search_ref_dir(dir, "refs/bisect/", 12);
                        if (pos < 0) {
                                struct ref_entry *child_entry;
-                               child_entry = create_dir_entry(dir->ref_cache,
+                               child_entry = create_dir_entry(dir->ref_store,
                                                               "refs/bisect/",
                                                               12, 1);
                                add_entry_to_dir(dir, child_entry);
@@ -261,13 +261,13 @@ static void clear_ref_dir(struct ref_dir *dir)
  * dirname is the name of the directory with a trailing slash (e.g.,
  * "refs/heads/") or "" for the top-level directory.
  */
-static struct ref_entry *create_dir_entry(struct ref_cache *ref_cache,
+static struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
                                          const char *dirname, size_t len,
                                          int incomplete)
 {
        struct ref_entry *direntry;
        FLEX_ALLOC_MEM(direntry, name, dirname, len);
-       direntry->u.subdir.ref_cache = ref_cache;
+       direntry->u.subdir.ref_store = ref_store;
        direntry->flag = REF_DIR | (incomplete ? REF_INCOMPLETE : 0);
        return direntry;
 }
@@ -343,7 +343,7 @@ static struct ref_dir *search_for_subdir(struct ref_dir *dir,
                 * therefore, create an empty record for it but mark
                 * the record complete.
                 */
-               entry = create_dir_entry(dir->ref_cache, subdirname, len, 0);
+               entry = create_dir_entry(dir->ref_store, subdirname, len, 0);
                add_entry_to_dir(dir, entry);
        } else {
                entry = dir->entries[entry_index];
@@ -501,7 +501,7 @@ static void sort_ref_dir(struct ref_dir *dir)
        if (dir->sorted == dir->nr)
                return;
 
-       qsort(dir->entries, dir->nr, sizeof(*dir->entries), ref_entry_cmp);
+       QSORT(dir->entries, dir->nr, ref_entry_cmp);
 
        /* Remove any duplicates: */
        for (i = 0, j = 0; j < dir->nr; j++) {
@@ -887,9 +887,9 @@ struct packed_ref_cache {
 
        /*
         * Count of references to the data structure in this instance,
-        * including the pointer from ref_cache::packed if any.  The
-        * data will not be freed as long as the reference count is
-        * nonzero.
+        * including the pointer from files_ref_store::packed if any.
+        * The data will not be freed as long as the reference count
+        * is nonzero.
         */
        unsigned int referrers;
 
@@ -910,17 +910,11 @@ struct packed_ref_cache {
  * Future: need to be in "struct repository"
  * when doing a full libification.
  */
-static struct ref_cache {
-       struct ref_cache *next;
+struct files_ref_store {
+       struct ref_store base;
        struct ref_entry *loose;
        struct packed_ref_cache *packed;
-       /*
-        * The submodule name, or "" for the main repo.  We allocate
-        * length 1 rather than FLEX_ARRAY so that the main ref_cache
-        * is initialized correctly.
-        */
-       char name[1];
-} ref_cache, *submodule_ref_caches;
+};
 
 /* Lock used for the main packed-refs file: */
 static struct lock_file packlock;
@@ -949,7 +943,7 @@ static int release_packed_ref_cache(struct packed_ref_cache *packed_refs)
        }
 }
 
-static void clear_packed_ref_cache(struct ref_cache *refs)
+static void clear_packed_ref_cache(struct files_ref_store *refs)
 {
        if (refs->packed) {
                struct packed_ref_cache *packed_refs = refs->packed;
@@ -961,7 +955,7 @@ static void clear_packed_ref_cache(struct ref_cache *refs)
        }
 }
 
-static void clear_loose_ref_cache(struct ref_cache *refs)
+static void clear_loose_ref_cache(struct files_ref_store *refs)
 {
        if (refs->loose) {
                free_ref_entry(refs->loose);
@@ -973,53 +967,34 @@ static void clear_loose_ref_cache(struct ref_cache *refs)
  * Create a new submodule ref cache and add it to the internal
  * set of caches.
  */
-static struct ref_cache *create_ref_cache(const char *submodule)
+static struct ref_store *files_ref_store_create(const char *submodule)
 {
-       struct ref_cache *refs;
-       if (!submodule)
-               submodule = "";
-       FLEX_ALLOC_STR(refs, name, submodule);
-       refs->next = submodule_ref_caches;
-       submodule_ref_caches = refs;
-       return refs;
-}
+       struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
+       struct ref_store *ref_store = (struct ref_store *)refs;
 
-static struct ref_cache *lookup_ref_cache(const char *submodule)
-{
-       struct ref_cache *refs;
-
-       if (!submodule || !*submodule)
-               return &ref_cache;
+       base_ref_store_init(ref_store, &refs_be_files, submodule);
 
-       for (refs = submodule_ref_caches; refs; refs = refs->next)
-               if (!strcmp(submodule, refs->name))
-                       return refs;
-       return NULL;
+       return ref_store;
 }
 
 /*
- * Return a pointer to a ref_cache for the specified submodule. For
- * the main repository, use submodule==NULL; such a call cannot fail.
- * For a submodule, the submodule must exist and be a nonbare
- * repository, otherwise return NULL.
- *
- * The returned structure will be allocated and initialized but not
- * necessarily populated; it should not be freed.
+ * Downcast ref_store to files_ref_store. Die if ref_store is not a
+ * files_ref_store. If submodule_allowed is not true, then also die if
+ * files_ref_store is for a submodule (i.e., not for the main
+ * repository). caller is used in any necessary error messages.
  */
-static struct ref_cache *get_ref_cache(const char *submodule)
+static struct files_ref_store *files_downcast(
+               struct ref_store *ref_store, int submodule_allowed,
+               const char *caller)
 {
-       struct ref_cache *refs = lookup_ref_cache(submodule);
+       if (ref_store->be != &refs_be_files)
+               die("BUG: ref_store is type \"%s\" not \"files\" in %s",
+                   ref_store->be->name, caller);
 
-       if (!refs) {
-               struct strbuf submodule_sb = STRBUF_INIT;
+       if (!submodule_allowed)
+               assert_main_repository(ref_store, caller);
 
-               strbuf_addstr(&submodule_sb, submodule);
-               if (is_nonbare_repository_dir(&submodule_sb))
-                       refs = create_ref_cache(submodule);
-               strbuf_release(&submodule_sb);
-       }
-
-       return refs;
+       return (struct files_ref_store *)ref_store;
 }
 
 /* The length of a peeled reference line in packed-refs, including EOL: */
@@ -1151,15 +1126,16 @@ static void read_packed_refs(FILE *f, struct ref_dir *dir)
 }
 
 /*
- * Get the packed_ref_cache for the specified ref_cache, creating it
- * if necessary.
+ * Get the packed_ref_cache for the specified files_ref_store,
+ * creating it if necessary.
  */
-static struct packed_ref_cache *get_packed_ref_cache(struct ref_cache *refs)
+static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *refs)
 {
        char *packed_refs_file;
 
-       if (*refs->name)
-               packed_refs_file = git_pathdup_submodule(refs->name, "packed-refs");
+       if (*refs->base.submodule)
+               packed_refs_file = git_pathdup_submodule(refs->base.submodule,
+                                                        "packed-refs");
        else
                packed_refs_file = git_pathdup("packed-refs");
 
@@ -1189,7 +1165,7 @@ static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_ca
        return get_ref_dir(packed_ref_cache->root);
 }
 
-static struct ref_dir *get_packed_refs(struct ref_cache *refs)
+static struct ref_dir *get_packed_refs(struct files_ref_store *refs)
 {
        return get_packed_ref_dir(get_packed_ref_cache(refs));
 }
@@ -1200,10 +1176,10 @@ static struct ref_dir *get_packed_refs(struct ref_cache *refs)
  * lock_packed_refs()).  To actually write the packed-refs file, call
  * commit_packed_refs().
  */
-static void add_packed_ref(const char *refname, const unsigned char *sha1)
+static void add_packed_ref(struct files_ref_store *refs,
+                          const char *refname, const unsigned char *sha1)
 {
-       struct packed_ref_cache *packed_ref_cache =
-               get_packed_ref_cache(&ref_cache);
+       struct packed_ref_cache *packed_ref_cache = get_packed_ref_cache(refs);
 
        if (!packed_ref_cache->lock)
                die("internal error: packed refs not locked");
@@ -1218,20 +1194,26 @@ static void add_packed_ref(const char *refname, const unsigned char *sha1)
  */
 static void read_loose_refs(const char *dirname, struct ref_dir *dir)
 {
-       struct ref_cache *refs = dir->ref_cache;
+       struct files_ref_store *refs = dir->ref_store;
        DIR *d;
        struct dirent *de;
        int dirnamelen = strlen(dirname);
        struct strbuf refname;
        struct strbuf path = STRBUF_INIT;
        size_t path_baselen;
+       int err = 0;
 
-       if (*refs->name)
-               strbuf_git_path_submodule(&path, refs->name, "%s", dirname);
+       if (*refs->base.submodule)
+               err = strbuf_git_path_submodule(&path, refs->base.submodule, "%s", dirname);
        else
                strbuf_git_path(&path, "%s", dirname);
        path_baselen = path.len;
 
+       if (err) {
+               strbuf_release(&path);
+               return;
+       }
+
        d = opendir(path.buf);
        if (!d) {
                strbuf_release(&path);
@@ -1262,10 +1244,10 @@ static void read_loose_refs(const char *dirname, struct ref_dir *dir)
                } else {
                        int read_ok;
 
-                       if (*refs->name) {
+                       if (*refs->base.submodule) {
                                hashclr(sha1);
                                flag = 0;
-                               read_ok = !resolve_gitlink_ref(refs->name,
+                               read_ok = !resolve_gitlink_ref(refs->base.submodule,
                                                               refname.buf, sha1);
                        } else {
                                read_ok = !read_ref_full(refname.buf,
@@ -1306,7 +1288,7 @@ static void read_loose_refs(const char *dirname, struct ref_dir *dir)
        closedir(d);
 }
 
-static struct ref_dir *get_loose_refs(struct ref_cache *refs)
+static struct ref_dir *get_loose_refs(struct files_ref_store *refs)
 {
        if (!refs->loose) {
                /*
@@ -1324,105 +1306,22 @@ static struct ref_dir *get_loose_refs(struct ref_cache *refs)
        return get_ref_dir(refs->loose);
 }
 
-#define MAXREFLEN (1024)
-
-/*
- * Called by resolve_gitlink_ref_recursive() after it failed to read
- * from the loose refs in ref_cache refs. Find <refname> in the
- * packed-refs file for the submodule.
- */
-static int resolve_gitlink_packed_ref(struct ref_cache *refs,
-                                     const char *refname, unsigned char *sha1)
-{
-       struct ref_entry *ref;
-       struct ref_dir *dir = get_packed_refs(refs);
-
-       ref = find_ref(dir, refname);
-       if (ref == NULL)
-               return -1;
-
-       hashcpy(sha1, ref->u.value.oid.hash);
-       return 0;
-}
-
-static int resolve_gitlink_ref_recursive(struct ref_cache *refs,
-                                        const char *refname, unsigned char *sha1,
-                                        int recursion)
-{
-       int fd, len;
-       char buffer[128], *p;
-       char *path;
-
-       if (recursion > SYMREF_MAXDEPTH || strlen(refname) > MAXREFLEN)
-               return -1;
-       path = *refs->name
-               ? git_pathdup_submodule(refs->name, "%s", refname)
-               : git_pathdup("%s", refname);
-       fd = open(path, O_RDONLY);
-       free(path);
-       if (fd < 0)
-               return resolve_gitlink_packed_ref(refs, refname, sha1);
-
-       len = read(fd, buffer, sizeof(buffer)-1);
-       close(fd);
-       if (len < 0)
-               return -1;
-       while (len && isspace(buffer[len-1]))
-               len--;
-       buffer[len] = 0;
-
-       /* Was it a detached head or an old-fashioned symlink? */
-       if (!get_sha1_hex(buffer, sha1))
-               return 0;
-
-       /* Symref? */
-       if (strncmp(buffer, "ref:", 4))
-               return -1;
-       p = buffer + 4;
-       while (isspace(*p))
-               p++;
-
-       return resolve_gitlink_ref_recursive(refs, p, sha1, recursion+1);
-}
-
-int resolve_gitlink_ref(const char *path, const char *refname, unsigned char *sha1)
-{
-       int len = strlen(path), retval;
-       struct strbuf submodule = STRBUF_INIT;
-       struct ref_cache *refs;
-
-       while (len && path[len-1] == '/')
-               len--;
-       if (!len)
-               return -1;
-
-       strbuf_add(&submodule, path, len);
-       refs = get_ref_cache(submodule.buf);
-       if (!refs) {
-               strbuf_release(&submodule);
-               return -1;
-       }
-       strbuf_release(&submodule);
-
-       retval = resolve_gitlink_ref_recursive(refs, refname, sha1, 0);
-       return retval;
-}
-
 /*
  * Return the ref_entry for the given refname from the packed
  * references.  If it does not exist, return NULL.
  */
-static struct ref_entry *get_packed_ref(const char *refname)
+static struct ref_entry *get_packed_ref(struct files_ref_store *refs,
+                                       const char *refname)
 {
-       return find_ref(get_packed_refs(&ref_cache), refname);
+       return find_ref(get_packed_refs(refs), refname);
 }
 
 /*
  * A loose ref file doesn't exist; check for a packed ref.
  */
-static int resolve_missing_loose_ref(const char *refname,
-                                    unsigned char *sha1,
-                                    unsigned int *flags)
+static int resolve_packed_ref(struct files_ref_store *refs,
+                             const char *refname,
+                             unsigned char *sha1, unsigned int *flags)
 {
        struct ref_entry *entry;
 
@@ -1430,7 +1329,7 @@ static int resolve_missing_loose_ref(const char *refname,
         * The loose reference file does not exist; check for a packed
         * reference.
         */
-       entry = get_packed_ref(refname);
+       entry = get_packed_ref(refs, refname);
        if (entry) {
                hashcpy(sha1, entry->u.value.oid.hash);
                *flags |= REF_ISPACKED;
@@ -1440,9 +1339,12 @@ static int resolve_missing_loose_ref(const char *refname,
        return -1;
 }
 
-int read_raw_ref(const char *refname, unsigned char *sha1,
-                struct strbuf *referent, unsigned int *type)
+static int files_read_raw_ref(struct ref_store *ref_store,
+                             const char *refname, unsigned char *sha1,
+                             struct strbuf *referent, unsigned int *type)
 {
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 1, "read_raw_ref");
        struct strbuf sb_contents = STRBUF_INIT;
        struct strbuf sb_path = STRBUF_INIT;
        const char *path;
@@ -1455,7 +1357,12 @@ int read_raw_ref(const char *refname, unsigned char *sha1,
 
        *type = 0;
        strbuf_reset(&sb_path);
-       strbuf_git_path(&sb_path, "%s", refname);
+
+       if (*refs->base.submodule)
+               strbuf_git_path_submodule(&sb_path, refs->base.submodule, "%s", refname);
+       else
+               strbuf_git_path(&sb_path, "%s", refname);
+
        path = sb_path.buf;
 
 stat_ref:
@@ -1478,7 +1385,7 @@ int read_raw_ref(const char *refname, unsigned char *sha1,
        if (lstat(path, &st) < 0) {
                if (errno != ENOENT)
                        goto out;
-               if (resolve_missing_loose_ref(refname, sha1, type)) {
+               if (resolve_packed_ref(refs, refname, sha1, type)) {
                        errno = ENOENT;
                        goto out;
                }
@@ -1517,7 +1424,7 @@ int read_raw_ref(const char *refname, unsigned char *sha1,
                 * ref is supposed to be, there could still be a
                 * packed ref:
                 */
-               if (resolve_missing_loose_ref(refname, sha1, type)) {
+               if (resolve_packed_ref(refs, refname, sha1, type)) {
                        errno = EISDIR;
                        goto out;
                }
@@ -1618,7 +1525,8 @@ static void unlock_ref(struct ref_lock *lock)
  *   avoided, namely if we were successfully able to read the ref
  * - Generate informative error messages in the case of failure
  */
-static int lock_raw_ref(const char *refname, int mustexist,
+static int lock_raw_ref(struct files_ref_store *refs,
+                       const char *refname, int mustexist,
                        const struct string_list *extras,
                        const struct string_list *skip,
                        struct ref_lock **lock_p,
@@ -1632,6 +1540,8 @@ static int lock_raw_ref(const char *refname, int mustexist,
        int ret = TRANSACTION_GENERIC_ERROR;
 
        assert(err);
+       assert_main_repository(&refs->base, "lock_raw_ref");
+
        *type = 0;
 
        /* First lock the file so it can't change out from under us. */
@@ -1715,7 +1625,8 @@ static int lock_raw_ref(const char *refname, int mustexist,
         * fear that its value will change.
         */
 
-       if (read_raw_ref(refname, lock->old_oid.hash, referent, type)) {
+       if (files_read_raw_ref(&refs->base, refname,
+                              lock->old_oid.hash, referent, type)) {
                if (errno == ENOENT) {
                        if (mustexist) {
                                /* Garden variety missing reference. */
@@ -1758,7 +1669,7 @@ static int lock_raw_ref(const char *refname, int mustexist,
                                                          REMOVE_DIR_EMPTY_ONLY)) {
                                if (verify_refname_available_dir(
                                                    refname, extras, skip,
-                                                   get_loose_refs(&ref_cache),
+                                                   get_loose_refs(refs),
                                                    err)) {
                                        /*
                                         * The error message set by
@@ -1797,7 +1708,7 @@ static int lock_raw_ref(const char *refname, int mustexist,
                 */
                if (verify_refname_available_dir(
                                    refname, extras, skip,
-                                   get_packed_refs(&ref_cache),
+                                   get_packed_refs(refs),
                                    err)) {
                        goto error_return;
                }
@@ -1850,8 +1761,10 @@ static enum peel_status peel_entry(struct ref_entry *entry, int repeel)
        return status;
 }
 
-int peel_ref(const char *refname, unsigned char *sha1)
+static int files_peel_ref(struct ref_store *ref_store,
+                         const char *refname, unsigned char *sha1)
 {
+       struct files_ref_store *refs = files_downcast(ref_store, 0, "peel_ref");
        int flag;
        unsigned char base[20];
 
@@ -1876,7 +1789,7 @@ int peel_ref(const char *refname, unsigned char *sha1)
         * have REF_KNOWS_PEELED.
         */
        if (flag & REF_ISPACKED) {
-               struct ref_entry *r = get_packed_ref(refname);
+               struct ref_entry *r = get_packed_ref(refs, refname);
                if (r) {
                        if (peel_entry(r, 0))
                                return -1;
@@ -1903,6 +1816,10 @@ static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
        int ok;
 
        while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
+               if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
+                   ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
+                       continue;
+
                if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&
                    !ref_resolves_to_object(iter->iter0->refname,
                                            iter->iter0->oid,
@@ -1951,11 +1868,12 @@ static struct ref_iterator_vtable files_ref_iterator_vtable = {
        files_ref_iterator_abort
 };
 
-struct ref_iterator *files_ref_iterator_begin(
-               const char *submodule,
+static struct ref_iterator *files_ref_iterator_begin(
+               struct ref_store *ref_store,
                const char *prefix, unsigned int flags)
 {
-       struct ref_cache *refs = get_ref_cache(submodule);
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 1, "ref_iterator_begin");
        struct ref_dir *loose_dir, *packed_dir;
        struct ref_iterator *loose_iter, *packed_iter;
        struct files_ref_iterator *iter;
@@ -2067,11 +1985,19 @@ static int remove_empty_directories(struct strbuf *path)
        return remove_dir_recursively(path, REMOVE_DIR_EMPTY_ONLY);
 }
 
+static int create_reflock(const char *path, void *cb)
+{
+       struct lock_file *lk = cb;
+
+       return hold_lock_file_for_update(lk, path, LOCK_NO_DEREF) < 0 ? -1 : 0;
+}
+
 /*
  * Locks a ref returning the lock on success and NULL on failure.
  * On failure errno is set to something meaningful.
  */
-static struct ref_lock *lock_ref_sha1_basic(const char *refname,
+static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
+                                           const char *refname,
                                            const unsigned char *old_sha1,
                                            const struct string_list *extras,
                                            const struct string_list *skip,
@@ -2081,12 +2007,11 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
        struct strbuf ref_file = STRBUF_INIT;
        struct ref_lock *lock;
        int last_errno = 0;
-       int lflags = LOCK_NO_DEREF;
        int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
        int resolve_flags = RESOLVE_REF_NO_RECURSE;
-       int attempts_remaining = 3;
        int resolved;
 
+       assert_main_repository(&refs->base, "lock_ref_sha1_basic");
        assert(err);
 
        lock = xcalloc(1, sizeof(struct ref_lock));
@@ -2108,8 +2033,9 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
                 */
                if (remove_empty_directories(&ref_file)) {
                        last_errno = errno;
-                       if (!verify_refname_available_dir(refname, extras, skip,
-                                                         get_loose_refs(&ref_cache), err))
+                       if (!verify_refname_available_dir(
+                                           refname, extras, skip,
+                                           get_loose_refs(refs), err))
                                strbuf_addf(err, "there are still refs under '%s'",
                                            refname);
                        goto error_return;
@@ -2120,8 +2046,9 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
        if (!resolved) {
                last_errno = errno;
                if (last_errno != ENOTDIR ||
-                   !verify_refname_available_dir(refname, extras, skip,
-                                                 get_loose_refs(&ref_cache), err))
+                   !verify_refname_available_dir(
+                                   refname, extras, skip,
+                                   get_loose_refs(refs), err))
                        strbuf_addf(err, "unable to resolve reference '%s': %s",
                                    refname, strerror(last_errno));
 
@@ -2136,7 +2063,8 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
         */
        if (is_null_oid(&lock->old_oid) &&
            verify_refname_available_dir(refname, extras, skip,
-                                        get_packed_refs(&ref_cache), err)) {
+                                        get_packed_refs(refs),
+                                        err)) {
                last_errno = ENOTDIR;
                goto error_return;
        }
@@ -2145,35 +2073,12 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 
        lock->ref_name = xstrdup(refname);
 
- retry:
-       switch (safe_create_leading_directories_const(ref_file.buf)) {
-       case SCLD_OK:
-               break; /* success */
-       case SCLD_VANISHED:
-               if (--attempts_remaining > 0)
-                       goto retry;
-               /* fall through */
-       default:
+       if (raceproof_create_file(ref_file.buf, create_reflock, lock->lk)) {
                last_errno = errno;
-               strbuf_addf(err, "unable to create directory for '%s'",
-                           ref_file.buf);
+               unable_to_lock_message(ref_file.buf, errno, err);
                goto error_return;
        }
 
-       if (hold_lock_file_for_update(lock->lk, ref_file.buf, lflags) < 0) {
-               last_errno = errno;
-               if (errno == ENOENT && --attempts_remaining > 0)
-                       /*
-                        * Maybe somebody just deleted one of the
-                        * directories leading to ref_file.  Try
-                        * again:
-                        */
-                       goto retry;
-               else {
-                       unable_to_lock_message(ref_file.buf, errno, err);
-                       goto error_return;
-               }
-       }
        if (verify_lock(lock, old_sha1, mustexist, err)) {
                last_errno = errno;
                goto error_return;
@@ -2223,13 +2128,14 @@ static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
  * hold_lock_file_for_update(). Return 0 on success. On errors, set
  * errno appropriately and return a nonzero value.
  */
-static int lock_packed_refs(int flags)
+static int lock_packed_refs(struct files_ref_store *refs, int flags)
 {
        static int timeout_configured = 0;
        static int timeout_value = 1000;
-
        struct packed_ref_cache *packed_ref_cache;
 
+       assert_main_repository(&refs->base, "lock_packed_refs");
+
        if (!timeout_configured) {
                git_config_get_int("core.packedrefstimeout", &timeout_value);
                timeout_configured = 1;
@@ -2245,7 +2151,7 @@ static int lock_packed_refs(int flags)
         * this will automatically invalidate the cache and re-read
         * the packed-refs file.
         */
-       packed_ref_cache = get_packed_ref_cache(&ref_cache);
+       packed_ref_cache = get_packed_ref_cache(refs);
        packed_ref_cache->lock = &packlock;
        /* Increment the reference count to prevent it from being freed: */
        acquire_packed_ref_cache(packed_ref_cache);
@@ -2258,14 +2164,16 @@ static int lock_packed_refs(int flags)
  * lock_packed_refs()). Return zero on success. On errors, set errno
  * and return a nonzero value
  */
-static int commit_packed_refs(void)
+static int commit_packed_refs(struct files_ref_store *refs)
 {
        struct packed_ref_cache *packed_ref_cache =
-               get_packed_ref_cache(&ref_cache);
+               get_packed_ref_cache(refs);
        int error = 0;
        int save_errno = 0;
        FILE *out;
 
+       assert_main_repository(&refs->base, "commit_packed_refs");
+
        if (!packed_ref_cache->lock)
                die("internal error: packed-refs not locked");
 
@@ -2292,17 +2200,19 @@ static int commit_packed_refs(void)
  * in-memory packed reference cache.  (The packed-refs file will be
  * read anew if it is needed again after this function is called.)
  */
-static void rollback_packed_refs(void)
+static void rollback_packed_refs(struct files_ref_store *refs)
 {
        struct packed_ref_cache *packed_ref_cache =
-               get_packed_ref_cache(&ref_cache);
+               get_packed_ref_cache(refs);
+
+       assert_main_repository(&refs->base, "rollback_packed_refs");
 
        if (!packed_ref_cache->lock)
                die("internal error: packed-refs not locked");
        rollback_lock_file(packed_ref_cache->lock);
        packed_ref_cache->lock = NULL;
        release_packed_ref_cache(packed_ref_cache);
-       clear_packed_ref_cache(&ref_cache);
+       clear_packed_ref_cache(refs);
 }
 
 struct ref_to_prune {
@@ -2372,13 +2282,15 @@ static int pack_if_possible_fn(struct ref_entry *entry, void *cb_data)
 
 /*
  * Remove empty parents, but spare refs/ and immediate subdirs.
- * Note: munges *name.
  */
-static void try_remove_empty_parents(char *name)
+static void try_remove_empty_parents(const char *refname)
 {
+       struct strbuf buf = STRBUF_INIT;
        char *p, *q;
        int i;
-       p = name;
+
+       strbuf_addstr(&buf, refname);
+       p = buf.buf;
        for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
                while (*p && *p != '/')
                        p++;
@@ -2386,8 +2298,7 @@ static void try_remove_empty_parents(char *name)
                while (*p == '/')
                        p++;
        }
-       for (q = p; *q; q++)
-               ;
+       q = buf.buf + buf.len;
        while (1) {
                while (q > p && *q != '/')
                        q--;
@@ -2395,10 +2306,11 @@ static void try_remove_empty_parents(char *name)
                        q--;
                if (q == p)
                        break;
-               *q = '\0';
-               if (rmdir(git_path("%s", name)))
+               strbuf_setlen(&buf, q - buf.buf);
+               if (rmdir(git_path("%s", buf.buf)))
                        break;
        }
+       strbuf_release(&buf);
 }
 
 /* make sure nobody touched the ref, and unlink */
@@ -2433,20 +2345,22 @@ static void prune_refs(struct ref_to_prune *r)
        }
 }
 
-int pack_refs(unsigned int flags)
+static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
 {
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 0, "pack_refs");
        struct pack_refs_cb_data cbdata;
 
        memset(&cbdata, 0, sizeof(cbdata));
        cbdata.flags = flags;
 
-       lock_packed_refs(LOCK_DIE_ON_ERROR);
-       cbdata.packed_refs = get_packed_refs(&ref_cache);
+       lock_packed_refs(refs, LOCK_DIE_ON_ERROR);
+       cbdata.packed_refs = get_packed_refs(refs);
 
-       do_for_each_entry_in_dir(get_loose_refs(&ref_cache), 0,
+       do_for_each_entry_in_dir(get_loose_refs(refs), 0,
                                 pack_if_possible_fn, &cbdata);
 
-       if (commit_packed_refs())
+       if (commit_packed_refs(refs))
                die_errno("unable to overwrite old ref-pack file");
 
        prune_refs(cbdata.ref_to_prune);
@@ -2460,17 +2374,19 @@ int pack_refs(unsigned int flags)
  *
  * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
  */
-static int repack_without_refs(struct string_list *refnames, struct strbuf *err)
+static int repack_without_refs(struct files_ref_store *refs,
+                              struct string_list *refnames, struct strbuf *err)
 {
        struct ref_dir *packed;
        struct string_list_item *refname;
        int ret, needs_repacking = 0, removed = 0;
 
+       assert_main_repository(&refs->base, "repack_without_refs");
        assert(err);
 
        /* Look for a packed ref */
        for_each_string_list_item(refname, refnames) {
-               if (get_packed_ref(refname->string)) {
+               if (get_packed_ref(refs, refname->string)) {
                        needs_repacking = 1;
                        break;
                }
@@ -2480,11 +2396,11 @@ static int repack_without_refs(struct string_list *refnames, struct strbuf *err)
        if (!needs_repacking)
                return 0; /* no refname exists in packed refs */
 
-       if (lock_packed_refs(0)) {
+       if (lock_packed_refs(refs, 0)) {
                unable_to_lock_message(git_path("packed-refs"), errno, err);
                return -1;
        }
-       packed = get_packed_refs(&ref_cache);
+       packed = get_packed_refs(refs);
 
        /* Remove refnames from the cache */
        for_each_string_list_item(refname, refnames)
@@ -2495,45 +2411,30 @@ static int repack_without_refs(struct string_list *refnames, struct strbuf *err)
                 * All packed entries disappeared while we were
                 * acquiring the lock.
                 */
-               rollback_packed_refs();
+               rollback_packed_refs(refs);
                return 0;
        }
 
        /* Write what remains */
-       ret = commit_packed_refs();
+       ret = commit_packed_refs(refs);
        if (ret)
                strbuf_addf(err, "unable to overwrite old ref-pack file: %s",
                            strerror(errno));
        return ret;
 }
 
-static int delete_ref_loose(struct ref_lock *lock, int flag, struct strbuf *err)
-{
-       assert(err);
-
-       if (!(flag & REF_ISPACKED) || flag & REF_ISSYMREF) {
-               /*
-                * loose.  The loose file name is the same as the
-                * lockfile name, minus ".lock":
-                */
-               char *loose_filename = get_locked_file_path(lock->lk);
-               int res = unlink_or_msg(loose_filename, err);
-               free(loose_filename);
-               if (res)
-                       return 1;
-       }
-       return 0;
-}
-
-int delete_refs(struct string_list *refnames, unsigned int flags)
+static int files_delete_refs(struct ref_store *ref_store,
+                            struct string_list *refnames, unsigned int flags)
 {
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 0, "delete_refs");
        struct strbuf err = STRBUF_INIT;
        int i, result = 0;
 
        if (!refnames->nr)
                return 0;
 
-       result = repack_without_refs(refnames, &err);
+       result = repack_without_refs(refs, refnames, &err);
        if (result) {
                /*
                 * If we failed to rewrite the packed-refs file, then
@@ -2572,65 +2473,56 @@ int delete_refs(struct string_list *refnames, unsigned int flags)
  */
 #define TMP_RENAMED_LOG  "logs/refs/.tmp-renamed-log"
 
-static int rename_tmp_log(const char *newrefname)
+static int rename_tmp_log_callback(const char *path, void *cb)
 {
-       int attempts_remaining = 4;
-       struct strbuf path = STRBUF_INIT;
-       int ret = -1;
+       int *true_errno = cb;
 
- retry:
-       strbuf_reset(&path);
-       strbuf_git_path(&path, "logs/%s", newrefname);
-       switch (safe_create_leading_directories_const(path.buf)) {
-       case SCLD_OK:
-               break; /* success */
-       case SCLD_VANISHED:
-               if (--attempts_remaining > 0)
-                       goto retry;
-               /* fall through */
-       default:
-               error("unable to create directory for %s", newrefname);
-               goto out;
+       if (rename(git_path(TMP_RENAMED_LOG), path)) {
+               /*
+                * rename(a, b) when b is an existing directory ought
+                * to result in ISDIR, but Solaris 5.8 gives ENOTDIR.
+                * Sheesh. Record the true errno for error reporting,
+                * but report EISDIR to raceproof_create_file() so
+                * that it knows to retry.
+                */
+               *true_errno = errno;
+               if (errno == ENOTDIR)
+                       errno = EISDIR;
+               return -1;
+       } else {
+               return 0;
        }
+}
 
-       if (rename(git_path(TMP_RENAMED_LOG), path.buf)) {
-               if ((errno==EISDIR || errno==ENOTDIR) && --attempts_remaining > 0) {
-                       /*
-                        * rename(a, b) when b is an existing
-                        * directory ought to result in ISDIR, but
-                        * Solaris 5.8 gives ENOTDIR.  Sheesh.
-                        */
-                       if (remove_empty_directories(&path)) {
-                               error("Directory not empty: logs/%s", newrefname);
-                               goto out;
-                       }
-                       goto retry;
-               } else if (errno == ENOENT && --attempts_remaining > 0) {
-                       /*
-                        * Maybe another process just deleted one of
-                        * the directories in the path to newrefname.
-                        * Try again from the beginning.
-                        */
-                       goto retry;
-               } else {
-                       error("unable to move logfile "TMP_RENAMED_LOG" to logs/%s: %s",
-                               newrefname, strerror(errno));
-                       goto out;
-               }
+static int rename_tmp_log(const char *newrefname)
+{
+       char *path = git_pathdup("logs/%s", newrefname);
+       int ret, true_errno;
+
+       ret = raceproof_create_file(path, rename_tmp_log_callback, &true_errno);
+       if (ret) {
+               if (errno == EISDIR)
+                       error("directory not empty: %s", path);
+               else
+                       error("unable to move logfile %s to %s: %s",
+                             git_path(TMP_RENAMED_LOG), path,
+                             strerror(true_errno));
        }
-       ret = 0;
-out:
-       strbuf_release(&path);
+
+       free(path);
        return ret;
 }
 
-int verify_refname_available(const char *newname,
-                            const struct string_list *extras,
-                            const struct string_list *skip,
-                            struct strbuf *err)
+static int files_verify_refname_available(struct ref_store *ref_store,
+                                         const char *newname,
+                                         const struct string_list *extras,
+                                         const struct string_list *skip,
+                                         struct strbuf *err)
 {
-       struct ref_dir *packed_refs = get_packed_refs(&ref_cache);
-       struct ref_dir *loose_refs = get_loose_refs(&ref_cache);
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 1, "verify_refname_available");
+       struct ref_dir *packed_refs = get_packed_refs(refs);
+       struct ref_dir *loose_refs = get_loose_refs(refs);
 
        if (verify_refname_available_dir(newname, extras, skip,
                                         packed_refs, err) ||
@@ -2643,12 +2535,17 @@ int verify_refname_available(const char *newname,
 
 static int write_ref_to_lockfile(struct ref_lock *lock,
                                 const unsigned char *sha1, struct strbuf *err);
-static int commit_ref_update(struct ref_lock *lock,
+static int commit_ref_update(struct files_ref_store *refs,
+                            struct ref_lock *lock,
                             const unsigned char *sha1, const char *logmsg,
                             struct strbuf *err);
 
-int rename_ref(const char *oldrefname, const char *newrefname, const char *logmsg)
+static int files_rename_ref(struct ref_store *ref_store,
+                           const char *oldrefname, const char *newrefname,
+                           const char *logmsg)
 {
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 0, "rename_ref");
        unsigned char sha1[20], orig_sha1[20];
        int flag = 0, logmoved = 0;
        struct ref_lock *lock;
@@ -2688,7 +2585,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
        if (!read_ref_full(newrefname, RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
                           sha1, NULL) &&
            delete_ref(newrefname, NULL, REF_NODEREF)) {
-               if (errno==EISDIR) {
+               if (errno == EISDIR) {
                        struct strbuf path = STRBUF_INIT;
                        int result;
 
@@ -2711,8 +2608,8 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 
        logmoved = log;
 
-       lock = lock_ref_sha1_basic(newrefname, NULL, NULL, NULL, REF_NODEREF,
-                                  NULL, &err);
+       lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
+                                  REF_NODEREF, NULL, &err);
        if (!lock) {
                error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
                strbuf_release(&err);
@@ -2721,7 +2618,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
        hashcpy(lock->old_oid.hash, orig_sha1);
 
        if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
-           commit_ref_update(lock, orig_sha1, logmsg, &err)) {
+           commit_ref_update(refs, lock, orig_sha1, logmsg, &err)) {
                error("unable to write current sha1 into %s: %s", newrefname, err.buf);
                strbuf_release(&err);
                goto rollback;
@@ -2730,8 +2627,8 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
        return 0;
 
  rollback:
-       lock = lock_ref_sha1_basic(oldrefname, NULL, NULL, NULL, REF_NODEREF,
-                                  NULL, &err);
+       lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
+                                  REF_NODEREF, NULL, &err);
        if (!lock) {
                error("unable to lock %s for rollback: %s", oldrefname, err.buf);
                strbuf_release(&err);
@@ -2741,7 +2638,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
        flag = log_all_ref_updates;
        log_all_ref_updates = 0;
        if (write_ref_to_lockfile(lock, orig_sha1, &err) ||
-           commit_ref_update(lock, orig_sha1, NULL, &err)) {
+           commit_ref_update(refs, lock, orig_sha1, NULL, &err)) {
                error("unable to write current sha1 into %s: %s", oldrefname, err.buf);
                strbuf_release(&err);
        }
@@ -2797,61 +2694,89 @@ static int commit_ref(struct ref_lock *lock)
        return 0;
 }
 
+static int open_or_create_logfile(const char *path, void *cb)
+{
+       int *fd = cb;
+
+       *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666);
+       return (*fd < 0) ? -1 : 0;
+}
+
 /*
- * Create a reflog for a ref.  If force_create = 0, the reflog will
- * only be created for certain refs (those for which
- * should_autocreate_reflog returns non-zero.  Otherwise, create it
- * regardless of the ref name.  Fill in *err and return -1 on failure.
+ * Create a reflog for a ref. If force_create = 0, only create the
+ * reflog for certain refs (those for which should_autocreate_reflog
+ * returns non-zero). Otherwise, create it regardless of the reference
+ * name. If the logfile already existed or was created, return 0 and
+ * set *logfd to the file descriptor opened for appending to the file.
+ * If no logfile exists and we decided not to create one, return 0 and
+ * set *logfd to -1. On failure, fill in *err, set *logfd to -1, and
+ * return -1.
  */
-static int log_ref_setup(const char *refname, struct strbuf *logfile, struct strbuf *err, int force_create)
+static int log_ref_setup(const char *refname, int force_create,
+                        int *logfd, struct strbuf *err)
 {
-       int logfd, oflags = O_APPEND | O_WRONLY;
+       char *logfile = git_pathdup("logs/%s", refname);
 
-       strbuf_git_path(logfile, "logs/%s", refname);
        if (force_create || should_autocreate_reflog(refname)) {
-               if (safe_create_leading_directories(logfile->buf) < 0) {
-                       strbuf_addf(err, "unable to create directory for '%s': "
-                                   "%s", logfile->buf, strerror(errno));
-                       return -1;
-               }
-               oflags |= O_CREAT;
-       }
-
-       logfd = open(logfile->buf, oflags, 0666);
-       if (logfd < 0) {
-               if (!(oflags & O_CREAT) && (errno == ENOENT || errno == EISDIR))
-                       return 0;
+               if (raceproof_create_file(logfile, open_or_create_logfile, logfd)) {
+                       if (errno == ENOENT)
+                               strbuf_addf(err, "unable to create directory for '%s': "
+                                           "%s", logfile, strerror(errno));
+                       else if (errno == EISDIR)
+                               strbuf_addf(err, "there are still logs under '%s'",
+                                           logfile);
+                       else
+                               strbuf_addf(err, "unable to append to '%s': %s",
+                                           logfile, strerror(errno));
 
-               if (errno == EISDIR) {
-                       if (remove_empty_directories(logfile)) {
-                               strbuf_addf(err, "there are still logs under "
-                                           "'%s'", logfile->buf);
-                               return -1;
-                       }
-                       logfd = open(logfile->buf, oflags, 0666);
+                       goto error;
                }
-
-               if (logfd < 0) {
-                       strbuf_addf(err, "unable to append to '%s': %s",
-                                   logfile->buf, strerror(errno));
-                       return -1;
+       } else {
+               *logfd = open(logfile, O_APPEND | O_WRONLY, 0666);
+               if (*logfd < 0) {
+                       if (errno == ENOENT || errno == EISDIR) {
+                               /*
+                                * The logfile doesn't already exist,
+                                * but that is not an error; it only
+                                * means that we won't write log
+                                * entries to it.
+                                */
+                               ;
+                       } else {
+                               strbuf_addf(err, "unable to append to '%s': %s",
+                                           logfile, strerror(errno));
+                               goto error;
+                       }
                }
        }
 
-       adjust_shared_perm(logfile->buf);
-       close(logfd);
+       if (*logfd >= 0)
+               adjust_shared_perm(logfile);
+
+       free(logfile);
        return 0;
-}
 
+error:
+       free(logfile);
+       return -1;
+}
 
-int safe_create_reflog(const char *refname, int force_create, struct strbuf *err)
+static int files_create_reflog(struct ref_store *ref_store,
+                              const char *refname, int force_create,
+                              struct strbuf *err)
 {
-       int ret;
-       struct strbuf sb = STRBUF_INIT;
+       int fd;
 
-       ret = log_ref_setup(refname, &sb, err, force_create);
-       strbuf_release(&sb);
-       return ret;
+       /* Check validity (but we don't need the result): */
+       files_downcast(ref_store, 0, "create_reflog");
+
+       if (log_ref_setup(refname, force_create, &fd, err))
+               return -1;
+
+       if (fd >= 0)
+               close(fd);
+
+       return 0;
 }
 
 static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
@@ -2880,59 +2805,43 @@ static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
        return 0;
 }
 
-static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
-                          const unsigned char *new_sha1, const char *msg,
-                          struct strbuf *logfile, int flags,
-                          struct strbuf *err)
+int files_log_ref_write(const char *refname, const unsigned char *old_sha1,
+                       const unsigned char *new_sha1, const char *msg,
+                       int flags, struct strbuf *err)
 {
-       int logfd, result, oflags = O_APPEND | O_WRONLY;
+       int logfd, result;
 
        if (log_all_ref_updates < 0)
                log_all_ref_updates = !is_bare_repository();
 
-       result = log_ref_setup(refname, logfile, err, flags & REF_FORCE_CREATE_REFLOG);
+       result = log_ref_setup(refname, flags & REF_FORCE_CREATE_REFLOG,
+                              &logfd, err);
 
        if (result)
                return result;
 
-       logfd = open(logfile->buf, oflags);
        if (logfd < 0)
                return 0;
        result = log_ref_write_fd(logfd, old_sha1, new_sha1,
                                  git_committer_info(0), msg);
        if (result) {
-               strbuf_addf(err, "unable to append to '%s': %s", logfile->buf,
-                           strerror(errno));
+               int save_errno = errno;
+
+               strbuf_addf(err, "unable to append to '%s': %s",
+                           git_path("logs/%s", refname), strerror(save_errno));
                close(logfd);
                return -1;
        }
        if (close(logfd)) {
-               strbuf_addf(err, "unable to append to '%s': %s", logfile->buf,
-                           strerror(errno));
+               int save_errno = errno;
+
+               strbuf_addf(err, "unable to append to '%s': %s",
+                           git_path("logs/%s", refname), strerror(save_errno));
                return -1;
        }
        return 0;
 }
 
-static int log_ref_write(const char *refname, const unsigned char *old_sha1,
-                        const unsigned char *new_sha1, const char *msg,
-                        int flags, struct strbuf *err)
-{
-       return files_log_ref_write(refname, old_sha1, new_sha1, msg, flags,
-                                  err);
-}
-
-int files_log_ref_write(const char *refname, const unsigned char *old_sha1,
-                       const unsigned char *new_sha1, const char *msg,
-                       int flags, struct strbuf *err)
-{
-       struct strbuf sb = STRBUF_INIT;
-       int ret = log_ref_write_1(refname, old_sha1, new_sha1, msg, &sb, flags,
-                                 err);
-       strbuf_release(&sb);
-       return ret;
-}
-
 /*
  * Write sha1 into the open lockfile, then close the lockfile. On
  * errors, rollback the lockfile, fill in *err and
@@ -2977,12 +2886,16 @@ static int write_ref_to_lockfile(struct ref_lock *lock,
  * to the loose reference lockfile. Also update the reflogs if
  * necessary, using the specified lockmsg (which can be NULL).
  */
-static int commit_ref_update(struct ref_lock *lock,
+static int commit_ref_update(struct files_ref_store *refs,
+                            struct ref_lock *lock,
                             const unsigned char *sha1, const char *logmsg,
                             struct strbuf *err)
 {
-       clear_loose_ref_cache(&ref_cache);
-       if (log_ref_write(lock->ref_name, lock->old_oid.hash, sha1, logmsg, 0, err)) {
+       assert_main_repository(&refs->base, "commit_ref_update");
+
+       clear_loose_ref_cache(refs);
+       if (files_log_ref_write(lock->ref_name, lock->old_oid.hash, sha1,
+                               logmsg, 0, err)) {
                char *old_msg = strbuf_detach(err, NULL);
                strbuf_addf(err, "cannot update the ref '%s': %s",
                            lock->ref_name, old_msg);
@@ -3013,7 +2926,7 @@ static int commit_ref_update(struct ref_lock *lock,
                if (head_ref && (head_flag & REF_ISSYMREF) &&
                    !strcmp(head_ref, lock->ref_name)) {
                        struct strbuf log_err = STRBUF_INIT;
-                       if (log_ref_write("HEAD", lock->old_oid.hash, sha1,
+                       if (files_log_ref_write("HEAD", lock->old_oid.hash, sha1,
                                          logmsg, 0, &log_err)) {
                                error("%s", log_err.buf);
                                strbuf_release(&log_err);
@@ -3052,7 +2965,8 @@ static void update_symref_reflog(struct ref_lock *lock, const char *refname,
        struct strbuf err = STRBUF_INIT;
        unsigned char new_sha1[20];
        if (logmsg && !read_ref(target, new_sha1) &&
-           log_ref_write(refname, lock->old_oid.hash, new_sha1, logmsg, 0, &err)) {
+           files_log_ref_write(refname, lock->old_oid.hash, new_sha1,
+                               logmsg, 0, &err)) {
                error("%s", err.buf);
                strbuf_release(&err);
        }
@@ -3080,13 +2994,18 @@ static int create_symref_locked(struct ref_lock *lock, const char *refname,
        return 0;
 }
 
-int create_symref(const char *refname, const char *target, const char *logmsg)
+static int files_create_symref(struct ref_store *ref_store,
+                              const char *refname, const char *target,
+                              const char *logmsg)
 {
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 0, "create_symref");
        struct strbuf err = STRBUF_INIT;
        struct ref_lock *lock;
        int ret;
 
-       lock = lock_ref_sha1_basic(refname, NULL, NULL, NULL, REF_NODEREF, NULL,
+       lock = lock_ref_sha1_basic(refs, refname, NULL,
+                                  NULL, NULL, REF_NODEREF, NULL,
                                   &err);
        if (!lock) {
                error("%s", err.buf);
@@ -3134,16 +3053,24 @@ int set_worktree_head_symref(const char *gitdir, const char *target)
        return ret;
 }
 
-int reflog_exists(const char *refname)
+static int files_reflog_exists(struct ref_store *ref_store,
+                              const char *refname)
 {
        struct stat st;
 
+       /* Check validity (but we don't need the result): */
+       files_downcast(ref_store, 0, "reflog_exists");
+
        return !lstat(git_path("logs/%s", refname), &st) &&
                S_ISREG(st.st_mode);
 }
 
-int delete_reflog(const char *refname)
+static int files_delete_reflog(struct ref_store *ref_store,
+                              const char *refname)
 {
+       /* Check validity (but we don't need the result): */
+       files_downcast(ref_store, 0, "delete_reflog");
+
        return remove_path(git_path("logs/%s", refname));
 }
 
@@ -3186,13 +3113,19 @@ static char *find_beginning_of_line(char *bob, char *scan)
        return scan;
 }
 
-int for_each_reflog_ent_reverse(const char *refname, each_reflog_ent_fn fn, void *cb_data)
+static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
+                                            const char *refname,
+                                            each_reflog_ent_fn fn,
+                                            void *cb_data)
 {
        struct strbuf sb = STRBUF_INIT;
        FILE *logfp;
        long pos;
        int ret = 0, at_tail = 1;
 
+       /* Check validity (but we don't need the result): */
+       files_downcast(ref_store, 0, "for_each_reflog_ent_reverse");
+
        logfp = fopen(git_path("logs/%s", refname), "r");
        if (!logfp)
                return -1;
@@ -3288,12 +3221,17 @@ int for_each_reflog_ent_reverse(const char *refname, each_reflog_ent_fn fn, void
        return ret;
 }
 
-int for_each_reflog_ent(const char *refname, each_reflog_ent_fn fn, void *cb_data)
+static int files_for_each_reflog_ent(struct ref_store *ref_store,
+                                    const char *refname,
+                                    each_reflog_ent_fn fn, void *cb_data)
 {
        FILE *logfp;
        struct strbuf sb = STRBUF_INIT;
        int ret = 0;
 
+       /* Check validity (but we don't need the result): */
+       files_downcast(ref_store, 0, "for_each_reflog_ent");
+
        logfp = fopen(git_path("logs/%s", refname), "r");
        if (!logfp)
                return -1;
@@ -3372,22 +3310,19 @@ static struct ref_iterator_vtable files_reflog_iterator_vtable = {
        files_reflog_iterator_abort
 };
 
-struct ref_iterator *files_reflog_iterator_begin(void)
+static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
 {
        struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
        struct ref_iterator *ref_iterator = &iter->base;
 
+       /* Check validity (but we don't need the result): */
+       files_downcast(ref_store, 0, "reflog_iterator_begin");
+
        base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
        iter->dir_iterator = dir_iterator_begin(git_path("logs"));
        return ref_iterator;
 }
 
-int for_each_reflog(each_ref_fn fn, void *cb_data)
-{
-       return do_for_each_ref_iterator(files_reflog_iterator_begin(),
-                                       fn, cb_data);
-}
-
 static int ref_update_reject_duplicates(struct string_list *refnames,
                                        struct strbuf *err)
 {
@@ -3460,7 +3395,8 @@ static int split_head_update(struct ref_update *update,
  * Note that the new update will itself be subject to splitting when
  * the iteration gets to it.
  */
-static int split_symref_update(struct ref_update *update,
+static int split_symref_update(struct files_ref_store *refs,
+                              struct ref_update *update,
                               const char *referent,
                               struct ref_transaction *transaction,
                               struct string_list *affected_refnames,
@@ -3574,7 +3510,8 @@ static int check_old_oid(struct ref_update *update, struct object_id *oid,
  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
  *   update of HEAD.
  */
-static int lock_ref_for_update(struct ref_update *update,
+static int lock_ref_for_update(struct files_ref_store *refs,
+                              struct ref_update *update,
                               struct ref_transaction *transaction,
                               const char *head_ref,
                               struct string_list *affected_refnames,
@@ -3586,6 +3523,8 @@ static int lock_ref_for_update(struct ref_update *update,
        int ret;
        struct ref_lock *lock;
 
+       assert_main_repository(&refs->base, "lock_ref_for_update");
+
        if ((update->flags & REF_HAVE_NEW) && is_null_sha1(update->new_sha1))
                update->flags |= REF_DELETING;
 
@@ -3596,11 +3535,10 @@ static int lock_ref_for_update(struct ref_update *update,
                        return ret;
        }
 
-       ret = lock_raw_ref(update->refname, mustexist,
+       ret = lock_raw_ref(refs, update->refname, mustexist,
                           affected_refnames, NULL,
-                          &update->lock, &referent,
+                          &lock, &referent,
                           &update->type, err);
-
        if (ret) {
                char *reason;
 
@@ -3611,7 +3549,7 @@ static int lock_ref_for_update(struct ref_update *update,
                return ret;
        }
 
-       lock = update->lock;
+       update->backend_data = lock;
 
        if (update->type & REF_ISSYMREF) {
                if (update->flags & REF_NODEREF) {
@@ -3639,7 +3577,8 @@ static int lock_ref_for_update(struct ref_update *update,
                         * of processing the split-off update, so we
                         * don't have to do it here.
                         */
-                       ret = split_symref_update(update, referent.buf, transaction,
+                       ret = split_symref_update(refs, update,
+                                                 referent.buf, transaction,
                                                  affected_refnames, err);
                        if (ret)
                                return ret;
@@ -3658,7 +3597,8 @@ static int lock_ref_for_update(struct ref_update *update,
                for (parent_update = update->parent_update;
                     parent_update;
                     parent_update = parent_update->parent_update) {
-                       oidcpy(&parent_update->lock->old_oid, &lock->old_oid);
+                       struct ref_lock *parent_lock = parent_update->backend_data;
+                       oidcpy(&parent_lock->old_oid, &lock->old_oid);
                }
        }
 
@@ -3679,7 +3619,7 @@ static int lock_ref_for_update(struct ref_update *update,
                         * The lock was freed upon failure of
                         * write_ref_to_lockfile():
                         */
-                       update->lock = NULL;
+                       update->backend_data = NULL;
                        strbuf_addf(err,
                                    "cannot update ref '%s': %s",
                                    update->refname, write_err);
@@ -3704,9 +3644,12 @@ static int lock_ref_for_update(struct ref_update *update,
        return 0;
 }
 
-int ref_transaction_commit(struct ref_transaction *transaction,
-                          struct strbuf *err)
+static int files_transaction_commit(struct ref_store *ref_store,
+                                   struct ref_transaction *transaction,
+                                   struct strbuf *err)
 {
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 0, "ref_transaction_commit");
        int ret = 0, i;
        struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
        struct string_list_item *ref_to_delete;
@@ -3785,8 +3728,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
        for (i = 0; i < transaction->nr; i++) {
                struct ref_update *update = transaction->updates[i];
 
-               ret = lock_ref_for_update(update, transaction, head_ref,
-                                         &affected_refnames, err);
+               ret = lock_ref_for_update(refs, update, transaction,
+                                         head_ref, &affected_refnames, err);
                if (ret)
                        goto cleanup;
        }
@@ -3794,30 +3737,32 @@ int ref_transaction_commit(struct ref_transaction *transaction,
        /* Perform updates first so live commits remain referenced */
        for (i = 0; i < transaction->nr; i++) {
                struct ref_update *update = transaction->updates[i];
-               struct ref_lock *lock = update->lock;
+               struct ref_lock *lock = update->backend_data;
 
                if (update->flags & REF_NEEDS_COMMIT ||
                    update->flags & REF_LOG_ONLY) {
-                       if (log_ref_write(lock->ref_name, lock->old_oid.hash,
-                                         update->new_sha1,
-                                         update->msg, update->flags, err)) {
+                       if (files_log_ref_write(lock->ref_name,
+                                               lock->old_oid.hash,
+                                               update->new_sha1,
+                                               update->msg, update->flags,
+                                               err)) {
                                char *old_msg = strbuf_detach(err, NULL);
 
                                strbuf_addf(err, "cannot update the ref '%s': %s",
                                            lock->ref_name, old_msg);
                                free(old_msg);
                                unlock_ref(lock);
-                               update->lock = NULL;
+                               update->backend_data = NULL;
                                ret = TRANSACTION_GENERIC_ERROR;
                                goto cleanup;
                        }
                }
                if (update->flags & REF_NEEDS_COMMIT) {
-                       clear_loose_ref_cache(&ref_cache);
+                       clear_loose_ref_cache(refs);
                        if (commit_ref(lock)) {
                                strbuf_addf(err, "couldn't set '%s'", lock->ref_name);
                                unlock_ref(lock);
-                               update->lock = NULL;
+                               update->backend_data = NULL;
                                ret = TRANSACTION_GENERIC_ERROR;
                                goto cleanup;
                        }
@@ -3826,34 +3771,39 @@ int ref_transaction_commit(struct ref_transaction *transaction,
        /* Perform deletes now that updates are safely completed */
        for (i = 0; i < transaction->nr; i++) {
                struct ref_update *update = transaction->updates[i];
+               struct ref_lock *lock = update->backend_data;
 
                if (update->flags & REF_DELETING &&
                    !(update->flags & REF_LOG_ONLY)) {
-                       if (delete_ref_loose(update->lock, update->type, err)) {
-                               ret = TRANSACTION_GENERIC_ERROR;
-                               goto cleanup;
+                       if (!(update->type & REF_ISPACKED) ||
+                           update->type & REF_ISSYMREF) {
+                               /* It is a loose reference. */
+                               if (unlink_or_msg(git_path("%s", lock->ref_name), err)) {
+                                       ret = TRANSACTION_GENERIC_ERROR;
+                                       goto cleanup;
+                               }
                        }
 
                        if (!(update->flags & REF_ISPRUNING))
                                string_list_append(&refs_to_delete,
-                                                  update->lock->ref_name);
+                                                  lock->ref_name);
                }
        }
 
-       if (repack_without_refs(&refs_to_delete, err)) {
+       if (repack_without_refs(refs, &refs_to_delete, err)) {
                ret = TRANSACTION_GENERIC_ERROR;
                goto cleanup;
        }
        for_each_string_list_item(ref_to_delete, &refs_to_delete)
                unlink_or_warn(git_path("logs/%s", ref_to_delete->string));
-       clear_loose_ref_cache(&ref_cache);
+       clear_loose_ref_cache(refs);
 
 cleanup:
        transaction->state = REF_TRANSACTION_CLOSED;
 
        for (i = 0; i < transaction->nr; i++)
-               if (transaction->updates[i]->lock)
-                       unlock_ref(transaction->updates[i]->lock);
+               if (transaction->updates[i]->backend_data)
+                       unlock_ref(transaction->updates[i]->backend_data);
        string_list_clear(&refs_to_delete, 0);
        free(head_ref);
        string_list_clear(&affected_refnames, 0);
@@ -3869,9 +3819,12 @@ static int ref_present(const char *refname,
        return string_list_has_string(affected_refnames, refname);
 }
 
-int initial_ref_transaction_commit(struct ref_transaction *transaction,
-                                  struct strbuf *err)
+static int files_initial_transaction_commit(struct ref_store *ref_store,
+                                           struct ref_transaction *transaction,
+                                           struct strbuf *err)
 {
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 0, "initial_ref_transaction_commit");
        int ret = 0, i;
        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
 
@@ -3919,7 +3872,7 @@ int initial_ref_transaction_commit(struct ref_transaction *transaction,
                }
        }
 
-       if (lock_packed_refs(0)) {
+       if (lock_packed_refs(refs, 0)) {
                strbuf_addf(err, "unable to lock packed-refs file: %s",
                            strerror(errno));
                ret = TRANSACTION_GENERIC_ERROR;
@@ -3931,10 +3884,10 @@ int initial_ref_transaction_commit(struct ref_transaction *transaction,
 
                if ((update->flags & REF_HAVE_NEW) &&
                    !is_null_sha1(update->new_sha1))
-                       add_packed_ref(update->refname, update->new_sha1);
+                       add_packed_ref(refs, update->refname, update->new_sha1);
        }
 
-       if (commit_packed_refs()) {
+       if (commit_packed_refs(refs)) {
                strbuf_addf(err, "unable to commit packed-refs file: %s",
                            strerror(errno));
                ret = TRANSACTION_GENERIC_ERROR;
@@ -3984,13 +3937,16 @@ static int expire_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
        return 0;
 }
 
-int reflog_expire(const char *refname, const unsigned char *sha1,
-                unsigned int flags,
-                reflog_expiry_prepare_fn prepare_fn,
-                reflog_expiry_should_prune_fn should_prune_fn,
-                reflog_expiry_cleanup_fn cleanup_fn,
-                void *policy_cb_data)
+static int files_reflog_expire(struct ref_store *ref_store,
+                              const char *refname, const unsigned char *sha1,
+                              unsigned int flags,
+                              reflog_expiry_prepare_fn prepare_fn,
+                              reflog_expiry_should_prune_fn should_prune_fn,
+                              reflog_expiry_cleanup_fn cleanup_fn,
+                              void *policy_cb_data)
 {
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 0, "reflog_expire");
        static struct lock_file reflog_lock;
        struct expire_reflog_cb cb;
        struct ref_lock *lock;
@@ -4009,7 +3965,8 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
         * reference itself, plus we might need to update the
         * reference if --updateref was specified:
         */
-       lock = lock_ref_sha1_basic(refname, sha1, NULL, NULL, REF_NODEREF,
+       lock = lock_ref_sha1_basic(refs, refname, sha1,
+                                  NULL, NULL, REF_NODEREF,
                                   &type, &err);
        if (!lock) {
                error("cannot lock ref '%s': %s", refname, err.buf);
@@ -4089,3 +4046,47 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
        unlock_ref(lock);
        return -1;
 }
+
+static int files_init_db(struct ref_store *ref_store, struct strbuf *err)
+{
+       /* Check validity (but we don't need the result): */
+       files_downcast(ref_store, 0, "init_db");
+
+       /*
+        * Create .git/refs/{heads,tags}
+        */
+       safe_create_dir(git_path("refs/heads"), 1);
+       safe_create_dir(git_path("refs/tags"), 1);
+       if (get_shared_repository()) {
+               adjust_shared_perm(git_path("refs/heads"));
+               adjust_shared_perm(git_path("refs/tags"));
+       }
+       return 0;
+}
+
+struct ref_storage_be refs_be_files = {
+       NULL,
+       "files",
+       files_ref_store_create,
+       files_init_db,
+       files_transaction_commit,
+       files_initial_transaction_commit,
+
+       files_pack_refs,
+       files_peel_ref,
+       files_create_symref,
+       files_delete_refs,
+       files_rename_ref,
+
+       files_ref_iterator_begin,
+       files_read_raw_ref,
+       files_verify_refname_available,
+
+       files_reflog_iterator_begin,
+       files_for_each_reflog_ent,
+       files_for_each_reflog_ent_reverse,
+       files_reflog_exists,
+       files_create_reflog,
+       files_delete_reflog,
+       files_reflog_expire
+};