Merge branch 'mh/ref-races'
"git pack-refs" that races with new ref creation or deletion have been susceptible to lossage of refs under right conditions, which has been tightened up. * mh/ref-races: for_each_ref: load all loose refs before packed refs get_packed_ref_cache: reload packed-refs file when it changes add a stat_validity struct Extract a struct stat_data from cache_entry packed_ref_cache: increment refcount when locked do_for_each_entry(): increment the packed refs cache refcount refs: manage lifetime of packed refs cache via reference counting refs: implement simple transactions for the packed-refs file refs: wrap the packed refs cache in a level of indirection pack_refs(): split creation of packed refs and entry writing repack_without_ref(): split list curation and entry writing
This commit is contained in:
Junio C Hamano
316
refs.c
316
refs.c
@ -749,6 +749,21 @@ static int do_for_each_entry_in_dirs(struct ref_dir *dir1,
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}
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}
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/*
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* Load all of the refs from the dir into our in-memory cache. The hard work
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* of loading loose refs is done by get_ref_dir(), so we just need to recurse
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* through all of the sub-directories. We do not even need to care about
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* sorting, as traversal order does not matter to us.
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*/
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static void prime_ref_dir(struct ref_dir *dir)
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{
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int i;
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for (i = 0; i < dir->nr; i++) {
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struct ref_entry *entry = dir->entries[i];
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if (entry->flag & REF_DIR)
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prime_ref_dir(get_ref_dir(entry));
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}
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}
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/*
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* Return true iff refname1 and refname2 conflict with each other.
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* Two reference names conflict if one of them exactly matches the
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@ -806,6 +821,30 @@ static int is_refname_available(const char *refname, const char *oldrefname,
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return 1;
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}
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struct packed_ref_cache {
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struct ref_entry *root;
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/*
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* Count of references to the data structure in this instance,
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* including the pointer from ref_cache::packed if any. The
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* data will not be freed as long as the reference count is
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* nonzero.
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*/
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unsigned int referrers;
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/*
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* Iff the packed-refs file associated with this instance is
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* currently locked for writing, this points at the associated
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* lock (which is owned by somebody else). The referrer count
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* is also incremented when the file is locked and decremented
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* when it is unlocked.
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*/
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struct lock_file *lock;
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/* The metadata from when this packed-refs cache was read */
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struct stat_validity validity;
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};
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/*
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* Future: need to be in "struct repository"
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* when doing a full libification.
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@ -813,7 +852,7 @@ static int is_refname_available(const char *refname, const char *oldrefname,
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static struct ref_cache {
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struct ref_cache *next;
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struct ref_entry *loose;
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struct ref_entry *packed;
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struct packed_ref_cache *packed;
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/*
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* The submodule name, or "" for the main repo. We allocate
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* length 1 rather than FLEX_ARRAY so that the main ref_cache
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@ -822,11 +861,42 @@ static struct ref_cache {
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char name[1];
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} ref_cache, *submodule_ref_caches;
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/* Lock used for the main packed-refs file: */
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static struct lock_file packlock;
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/*
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* Increment the reference count of *packed_refs.
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*/
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static void acquire_packed_ref_cache(struct packed_ref_cache *packed_refs)
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{
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packed_refs->referrers++;
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}
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/*
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* Decrease the reference count of *packed_refs. If it goes to zero,
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* free *packed_refs and return true; otherwise return false.
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*/
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static int release_packed_ref_cache(struct packed_ref_cache *packed_refs)
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{
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if (!--packed_refs->referrers) {
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free_ref_entry(packed_refs->root);
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stat_validity_clear(&packed_refs->validity);
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free(packed_refs);
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return 1;
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} else {
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return 0;
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}
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}
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static void clear_packed_ref_cache(struct ref_cache *refs)
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{
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if (refs->packed) {
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free_ref_entry(refs->packed);
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struct packed_ref_cache *packed_refs = refs->packed;
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if (packed_refs->lock)
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die("internal error: packed-ref cache cleared while locked");
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refs->packed = NULL;
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release_packed_ref_cache(packed_refs);
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}
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}
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@ -996,29 +1066,57 @@ static void read_packed_refs(FILE *f, struct ref_dir *dir)
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}
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}
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static struct ref_dir *get_packed_refs(struct ref_cache *refs)
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/*
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* Get the packed_ref_cache for the specified ref_cache, creating it
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* if necessary.
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*/
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static struct packed_ref_cache *get_packed_ref_cache(struct ref_cache *refs)
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{
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const char *packed_refs_file;
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if (*refs->name)
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packed_refs_file = git_path_submodule(refs->name, "packed-refs");
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else
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packed_refs_file = git_path("packed-refs");
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if (refs->packed &&
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!stat_validity_check(&refs->packed->validity, packed_refs_file))
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clear_packed_ref_cache(refs);
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if (!refs->packed) {
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const char *packed_refs_file;
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FILE *f;
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refs->packed = create_dir_entry(refs, "", 0, 0);
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if (*refs->name)
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packed_refs_file = git_path_submodule(refs->name, "packed-refs");
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else
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packed_refs_file = git_path("packed-refs");
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refs->packed = xcalloc(1, sizeof(*refs->packed));
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acquire_packed_ref_cache(refs->packed);
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refs->packed->root = create_dir_entry(refs, "", 0, 0);
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f = fopen(packed_refs_file, "r");
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if (f) {
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read_packed_refs(f, get_ref_dir(refs->packed));
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stat_validity_update(&refs->packed->validity, fileno(f));
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read_packed_refs(f, get_ref_dir(refs->packed->root));
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fclose(f);
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}
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}
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return get_ref_dir(refs->packed);
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return refs->packed;
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}
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static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_cache)
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{
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return get_ref_dir(packed_ref_cache->root);
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}
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static struct ref_dir *get_packed_refs(struct ref_cache *refs)
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{
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return get_packed_ref_dir(get_packed_ref_cache(refs));
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}
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void add_packed_ref(const char *refname, const unsigned char *sha1)
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{
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add_ref(get_packed_refs(&ref_cache),
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struct packed_ref_cache *packed_ref_cache =
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get_packed_ref_cache(&ref_cache);
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if (!packed_ref_cache->lock)
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die("internal error: packed refs not locked");
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add_ref(get_packed_ref_dir(packed_ref_cache),
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create_ref_entry(refname, sha1, REF_ISPACKED, 1));
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}
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@ -1558,13 +1656,31 @@ void warn_dangling_symref(FILE *fp, const char *msg_fmt, const char *refname)
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static int do_for_each_entry(struct ref_cache *refs, const char *base,
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each_ref_entry_fn fn, void *cb_data)
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{
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struct ref_dir *packed_dir = get_packed_refs(refs);
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struct ref_dir *loose_dir = get_loose_refs(refs);
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struct packed_ref_cache *packed_ref_cache;
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struct ref_dir *loose_dir;
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struct ref_dir *packed_dir;
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int retval = 0;
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/*
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* We must make sure that all loose refs are read before accessing the
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* packed-refs file; this avoids a race condition in which loose refs
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* are migrated to the packed-refs file by a simultaneous process, but
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* our in-memory view is from before the migration. get_packed_ref_cache()
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* takes care of making sure our view is up to date with what is on
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* disk.
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*/
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loose_dir = get_loose_refs(refs);
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if (base && *base) {
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loose_dir = find_containing_dir(loose_dir, base, 0);
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}
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if (loose_dir)
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prime_ref_dir(loose_dir);
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packed_ref_cache = get_packed_ref_cache(refs);
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acquire_packed_ref_cache(packed_ref_cache);
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packed_dir = get_packed_ref_dir(packed_ref_cache);
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if (base && *base) {
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packed_dir = find_containing_dir(packed_dir, base, 0);
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loose_dir = find_containing_dir(loose_dir, base, 0);
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}
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if (packed_dir && loose_dir) {
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@ -1582,6 +1698,7 @@ static int do_for_each_entry(struct ref_cache *refs, const char *base,
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loose_dir, 0, fn, cb_data);
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}
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release_packed_ref_cache(packed_ref_cache);
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return retval;
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}
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@ -2036,6 +2153,73 @@ static void write_packed_entry(int fd, char *refname, unsigned char *sha1,
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}
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}
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/*
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* An each_ref_entry_fn that writes the entry to a packed-refs file.
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*/
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static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
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{
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int *fd = cb_data;
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enum peel_status peel_status = peel_entry(entry, 0);
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if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
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error("internal error: %s is not a valid packed reference!",
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entry->name);
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write_packed_entry(*fd, entry->name, entry->u.value.sha1,
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peel_status == PEEL_PEELED ?
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entry->u.value.peeled : NULL);
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return 0;
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}
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int lock_packed_refs(int flags)
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{
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struct packed_ref_cache *packed_ref_cache;
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/* Discard the old cache because it might be invalid: */
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clear_packed_ref_cache(&ref_cache);
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if (hold_lock_file_for_update(&packlock, git_path("packed-refs"), flags) < 0)
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return -1;
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/* Read the current packed-refs while holding the lock: */
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packed_ref_cache = get_packed_ref_cache(&ref_cache);
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packed_ref_cache->lock = &packlock;
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/* Increment the reference count to prevent it from being freed: */
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acquire_packed_ref_cache(packed_ref_cache);
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return 0;
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}
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int commit_packed_refs(void)
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{
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struct packed_ref_cache *packed_ref_cache =
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get_packed_ref_cache(&ref_cache);
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int error = 0;
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if (!packed_ref_cache->lock)
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die("internal error: packed-refs not locked");
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write_or_die(packed_ref_cache->lock->fd,
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PACKED_REFS_HEADER, strlen(PACKED_REFS_HEADER));
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do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
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0, write_packed_entry_fn,
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&packed_ref_cache->lock->fd);
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if (commit_lock_file(packed_ref_cache->lock))
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error = -1;
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packed_ref_cache->lock = NULL;
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release_packed_ref_cache(packed_ref_cache);
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return error;
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}
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void rollback_packed_refs(void)
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{
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struct packed_ref_cache *packed_ref_cache =
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get_packed_ref_cache(&ref_cache);
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if (!packed_ref_cache->lock)
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die("internal error: packed-refs not locked");
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rollback_lock_file(packed_ref_cache->lock);
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packed_ref_cache->lock = NULL;
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release_packed_ref_cache(packed_ref_cache);
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clear_packed_ref_cache(&ref_cache);
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}
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struct ref_to_prune {
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struct ref_to_prune *next;
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unsigned char sha1[20];
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@ -2044,35 +2228,50 @@ struct ref_to_prune {
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struct pack_refs_cb_data {
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unsigned int flags;
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struct ref_dir *packed_refs;
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struct ref_to_prune *ref_to_prune;
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int fd;
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};
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static int pack_one_ref(struct ref_entry *entry, void *cb_data)
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/*
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* An each_ref_entry_fn that is run over loose references only. If
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* the loose reference can be packed, add an entry in the packed ref
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* cache. If the reference should be pruned, also add it to
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* ref_to_prune in the pack_refs_cb_data.
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*/
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static int pack_if_possible_fn(struct ref_entry *entry, void *cb_data)
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{
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struct pack_refs_cb_data *cb = cb_data;
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enum peel_status peel_status;
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struct ref_entry *packed_entry;
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int is_tag_ref = !prefixcmp(entry->name, "refs/tags/");
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/* ALWAYS pack refs that were already packed or are tags */
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if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref &&
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!(entry->flag & REF_ISPACKED))
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/* ALWAYS pack tags */
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if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref)
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return 0;
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/* Do not pack symbolic or broken refs: */
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if ((entry->flag & REF_ISSYMREF) || !ref_resolves_to_object(entry))
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return 0;
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/* Add a packed ref cache entry equivalent to the loose entry. */
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peel_status = peel_entry(entry, 1);
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if (peel_status != PEEL_PEELED && peel_status != PEEL_NON_TAG)
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die("internal error peeling reference %s (%s)",
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entry->name, sha1_to_hex(entry->u.value.sha1));
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write_packed_entry(cb->fd, entry->name, entry->u.value.sha1,
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peel_status == PEEL_PEELED ?
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entry->u.value.peeled : NULL);
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packed_entry = find_ref(cb->packed_refs, entry->name);
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if (packed_entry) {
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/* Overwrite existing packed entry with info from loose entry */
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packed_entry->flag = REF_ISPACKED | REF_KNOWS_PEELED;
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hashcpy(packed_entry->u.value.sha1, entry->u.value.sha1);
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} else {
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packed_entry = create_ref_entry(entry->name, entry->u.value.sha1,
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REF_ISPACKED | REF_KNOWS_PEELED, 0);
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add_ref(cb->packed_refs, packed_entry);
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}
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hashcpy(packed_entry->u.value.peeled, entry->u.value.peeled);
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/* If the ref was already packed, there is no need to prune it. */
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if ((cb->flags & PACK_REFS_PRUNE) && !(entry->flag & REF_ISPACKED)) {
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/* Schedule the loose reference for pruning if requested. */
|
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if ((cb->flags & PACK_REFS_PRUNE)) {
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int namelen = strlen(entry->name) + 1;
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struct ref_to_prune *n = xcalloc(1, sizeof(*n) + namelen);
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hashcpy(n->sha1, entry->u.value.sha1);
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@ -2134,8 +2333,6 @@ static void prune_refs(struct ref_to_prune *r)
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}
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}
|
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|
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static struct lock_file packlock;
|
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|
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int pack_refs(unsigned int flags)
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{
|
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struct pack_refs_cb_data cbdata;
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@ -2143,26 +2340,38 @@ int pack_refs(unsigned int flags)
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memset(&cbdata, 0, sizeof(cbdata));
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cbdata.flags = flags;
|
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cbdata.fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"),
|
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LOCK_DIE_ON_ERROR);
|
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lock_packed_refs(LOCK_DIE_ON_ERROR);
|
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cbdata.packed_refs = get_packed_refs(&ref_cache);
|
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|
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write_or_die(cbdata.fd, PACKED_REFS_HEADER, strlen(PACKED_REFS_HEADER));
|
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do_for_each_entry_in_dir(get_loose_refs(&ref_cache), 0,
|
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pack_if_possible_fn, &cbdata);
|
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|
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do_for_each_entry(&ref_cache, "", pack_one_ref, &cbdata);
|
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if (commit_lock_file(&packlock) < 0)
|
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if (commit_packed_refs())
|
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die_errno("unable to overwrite old ref-pack file");
|
||||
|
||||
prune_refs(cbdata.ref_to_prune);
|
||||
return 0;
|
||||
}
|
||||
|
||||
static int repack_ref_fn(struct ref_entry *entry, void *cb_data)
|
||||
/*
|
||||
* If entry is no longer needed in packed-refs, add it to the string
|
||||
* list pointed to by cb_data. Reasons for deleting entries:
|
||||
*
|
||||
* - Entry is broken.
|
||||
* - Entry is overridden by a loose ref.
|
||||
* - Entry does not point at a valid object.
|
||||
*
|
||||
* In the first and third cases, also emit an error message because these
|
||||
* are indications of repository corruption.
|
||||
*/
|
||||
static int curate_packed_ref_fn(struct ref_entry *entry, void *cb_data)
|
||||
{
|
||||
int *fd = cb_data;
|
||||
enum peel_status peel_status;
|
||||
struct string_list *refs_to_delete = cb_data;
|
||||
|
||||
if (entry->flag & REF_ISBROKEN) {
|
||||
/* This shouldn't happen to packed refs. */
|
||||
error("%s is broken!", entry->name);
|
||||
string_list_append(refs_to_delete, entry->name);
|
||||
return 0;
|
||||
}
|
||||
if (!has_sha1_file(entry->u.value.sha1)) {
|
||||
@ -2172,7 +2381,7 @@ static int repack_ref_fn(struct ref_entry *entry, void *cb_data)
|
||||
if (read_ref_full(entry->name, sha1, 0, &flags))
|
||||
/* We should at least have found the packed ref. */
|
||||
die("Internal error");
|
||||
if ((flags & REF_ISSYMREF) || !(flags & REF_ISPACKED))
|
||||
if ((flags & REF_ISSYMREF) || !(flags & REF_ISPACKED)) {
|
||||
/*
|
||||
* This packed reference is overridden by a
|
||||
* loose reference, so it is OK that its value
|
||||
@ -2181,9 +2390,11 @@ static int repack_ref_fn(struct ref_entry *entry, void *cb_data)
|
||||
* collected. For this purpose we don't even
|
||||
* care whether the loose reference itself is
|
||||
* invalid, broken, symbolic, etc. Silently
|
||||
* omit the packed reference from the output.
|
||||
* remove the packed reference.
|
||||
*/
|
||||
string_list_append(refs_to_delete, entry->name);
|
||||
return 0;
|
||||
}
|
||||
/*
|
||||
* There is no overriding loose reference, so the fact
|
||||
* that this reference doesn't refer to a valid object
|
||||
@ -2192,44 +2403,47 @@ static int repack_ref_fn(struct ref_entry *entry, void *cb_data)
|
||||
* the output.
|
||||
*/
|
||||
error("%s does not point to a valid object!", entry->name);
|
||||
string_list_append(refs_to_delete, entry->name);
|
||||
return 0;
|
||||
}
|
||||
|
||||
peel_status = peel_entry(entry, 0);
|
||||
write_packed_entry(*fd, entry->name, entry->u.value.sha1,
|
||||
peel_status == PEEL_PEELED ?
|
||||
entry->u.value.peeled : NULL);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
static int repack_without_ref(const char *refname)
|
||||
{
|
||||
int fd;
|
||||
struct ref_dir *packed;
|
||||
struct string_list refs_to_delete = STRING_LIST_INIT_DUP;
|
||||
struct string_list_item *ref_to_delete;
|
||||
|
||||
if (!get_packed_ref(refname))
|
||||
return 0; /* refname does not exist in packed refs */
|
||||
|
||||
fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"), 0);
|
||||
if (fd < 0) {
|
||||
if (lock_packed_refs(0)) {
|
||||
unable_to_lock_error(git_path("packed-refs"), errno);
|
||||
return error("cannot delete '%s' from packed refs", refname);
|
||||
}
|
||||
clear_packed_ref_cache(&ref_cache);
|
||||
packed = get_packed_refs(&ref_cache);
|
||||
/* Remove refname from the cache. */
|
||||
|
||||
/* Remove refname from the cache: */
|
||||
if (remove_entry(packed, refname) == -1) {
|
||||
/*
|
||||
* The packed entry disappeared while we were
|
||||
* acquiring the lock.
|
||||
*/
|
||||
rollback_lock_file(&packlock);
|
||||
rollback_packed_refs();
|
||||
return 0;
|
||||
}
|
||||
write_or_die(fd, PACKED_REFS_HEADER, strlen(PACKED_REFS_HEADER));
|
||||
do_for_each_entry_in_dir(packed, 0, repack_ref_fn, &fd);
|
||||
return commit_lock_file(&packlock);
|
||||
|
||||
/* Remove any other accumulated cruft: */
|
||||
do_for_each_entry_in_dir(packed, 0, curate_packed_ref_fn, &refs_to_delete);
|
||||
for_each_string_list_item(ref_to_delete, &refs_to_delete) {
|
||||
if (remove_entry(packed, ref_to_delete->string) == -1)
|
||||
die("internal error");
|
||||
}
|
||||
|
||||
/* Write what remains: */
|
||||
return commit_packed_refs();
|
||||
}
|
||||
|
||||
int delete_ref(const char *refname, const unsigned char *sha1, int delopt)
|
||||
|
||||
Reference in New Issue
Block a user