Merge branch 'ag/rebase-i-in-c' into js/rebase-in-c-5.5-work-with-rebase-i-in-c
[gitweb.git] / refs / files-backend.c
index f21a954ce712bb06aae3b83992e20910dc6b061c..b9eb3aabe6388a6437109439c3ac2ca298853892 100644 (file)
 #include "../refs.h"
 #include "refs-internal.h"
 #include "ref-cache.h"
+#include "packed-backend.h"
 #include "../iterator.h"
 #include "../dir-iterator.h"
 #include "../lockfile.h"
 #include "../object.h"
 #include "../dir.h"
+#include "../chdir-notify.h"
 
-struct ref_lock {
-       char *ref_name;
-       struct lock_file *lk;
-       struct object_id old_oid;
-};
+/*
+ * This backend uses the following flags in `ref_update::flags` for
+ * internal bookkeeping purposes. Their numerical values must not
+ * conflict with REF_NO_DEREF, REF_FORCE_CREATE_REFLOG, REF_HAVE_NEW,
+ * REF_HAVE_OLD, or REF_IS_PRUNING, which are also stored in
+ * `ref_update::flags`.
+ */
 
 /*
- * Return true if refname, which has the specified oid and flags, can
- * be resolved to an object in the database. If the referred-to object
- * does not exist, emit a warning and return false.
+ * Used as a flag in ref_update::flags when a loose ref is being
+ * pruned. This flag must only be used when REF_NO_DEREF is set.
  */
-static int ref_resolves_to_object(const char *refname,
-                                 const struct object_id *oid,
-                                 unsigned int flags)
-{
-       if (flags & REF_ISBROKEN)
-               return 0;
-       if (!has_sha1_file(oid->hash)) {
-               error("%s does not point to a valid object!", refname);
-               return 0;
-       }
-       return 1;
-}
+#define REF_IS_PRUNING (1 << 4)
+
+/*
+ * Flag passed to lock_ref_sha1_basic() telling it to tolerate broken
+ * refs (i.e., because the reference is about to be deleted anyway).
+ */
+#define REF_DELETING (1 << 5)
 
-struct packed_ref_cache {
-       struct ref_cache *cache;
+/*
+ * Used as a flag in ref_update::flags when the lockfile needs to be
+ * committed.
+ */
+#define REF_NEEDS_COMMIT (1 << 6)
 
-       /*
-        * Count of references to the data structure in this instance,
-        * 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;
+/*
+ * Used as a flag in ref_update::flags when we want to log a ref
+ * update but not actually perform it.  This is used when a symbolic
+ * ref update is split up.
+ */
+#define REF_LOG_ONLY (1 << 7)
 
-       /* The metadata from when this packed-refs cache was read */
-       struct stat_validity validity;
-};
+/*
+ * Used as a flag in ref_update::flags when the ref_update was via an
+ * update to HEAD.
+ */
+#define REF_UPDATE_VIA_HEAD (1 << 8)
 
 /*
- * Future: need to be in "struct repository"
- * when doing a full libification.
+ * Used as a flag in ref_update::flags when the loose reference has
+ * been deleted.
  */
+#define REF_DELETED_LOOSE (1 << 9)
+
+struct ref_lock {
+       char *ref_name;
+       struct lock_file lk;
+       struct object_id old_oid;
+};
+
 struct files_ref_store {
        struct ref_store base;
        unsigned int store_flags;
 
        char *gitdir;
        char *gitcommondir;
-       char *packed_refs_path;
 
        struct ref_cache *loose;
-       struct packed_ref_cache *packed;
 
-       /*
-        * Lock used for the "packed-refs" file. Note that this (and
-        * thus the enclosing `files_ref_store`) must not be freed.
-        */
-       struct lock_file packed_refs_lock;
+       struct ref_store *packed_ref_store;
 };
 
-/*
- * Increment the reference count of *packed_refs.
- */
-static void acquire_packed_ref_cache(struct packed_ref_cache *packed_refs)
-{
-       packed_refs->referrers++;
-}
-
-/*
- * Decrease the reference count of *packed_refs.  If it goes to zero,
- * free *packed_refs and return true; otherwise return false.
- */
-static int release_packed_ref_cache(struct packed_ref_cache *packed_refs)
-{
-       if (!--packed_refs->referrers) {
-               free_ref_cache(packed_refs->cache);
-               stat_validity_clear(&packed_refs->validity);
-               free(packed_refs);
-               return 1;
-       } else {
-               return 0;
-       }
-}
-
-static void clear_packed_ref_cache(struct files_ref_store *refs)
-{
-       if (refs->packed) {
-               struct packed_ref_cache *packed_refs = refs->packed;
-
-               if (is_lock_file_locked(&refs->packed_refs_lock))
-                       die("BUG: packed-ref cache cleared while locked");
-               refs->packed = NULL;
-               release_packed_ref_cache(packed_refs);
-       }
-}
-
 static void clear_loose_ref_cache(struct files_ref_store *refs)
 {
        if (refs->loose) {
@@ -132,7 +100,13 @@ static struct ref_store *files_ref_store_create(const char *gitdir,
        get_common_dir_noenv(&sb, gitdir);
        refs->gitcommondir = strbuf_detach(&sb, NULL);
        strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
-       refs->packed_refs_path = strbuf_detach(&sb, NULL);
+       refs->packed_ref_store = packed_ref_store_create(sb.buf, flags);
+       strbuf_release(&sb);
+
+       chdir_notify_reparent("files-backend $GIT_DIR",
+                             &refs->gitdir);
+       chdir_notify_reparent("files-backend $GIT_COMMONDIR",
+                             &refs->gitcommondir);
 
        return ref_store;
 }
@@ -147,7 +121,7 @@ static void files_assert_main_repository(struct files_ref_store *refs,
        if (refs->store_flags & REF_STORE_MAIN)
                return;
 
-       die("BUG: operation %s only allowed for main ref store", caller);
+       BUG("operation %s only allowed for main ref store", caller);
 }
 
 /*
@@ -163,181 +137,22 @@ static struct files_ref_store *files_downcast(struct ref_store *ref_store,
        struct files_ref_store *refs;
 
        if (ref_store->be != &refs_be_files)
-               die("BUG: ref_store is type \"%s\" not \"files\" in %s",
+               BUG("ref_store is type \"%s\" not \"files\" in %s",
                    ref_store->be->name, caller);
 
        refs = (struct files_ref_store *)ref_store;
 
        if ((refs->store_flags & required_flags) != required_flags)
-               die("BUG: operation %s requires abilities 0x%x, but only have 0x%x",
+               BUG("operation %s requires abilities 0x%x, but only have 0x%x",
                    caller, required_flags, refs->store_flags);
 
        return refs;
 }
 
-/* The length of a peeled reference line in packed-refs, including EOL: */
-#define PEELED_LINE_LENGTH 42
-
-/*
- * The packed-refs header line that we write out.  Perhaps other
- * traits will be added later.  The trailing space is required.
- */
-static const char PACKED_REFS_HEADER[] =
-       "# pack-refs with: peeled fully-peeled \n";
-
-/*
- * Parse one line from a packed-refs file.  Write the SHA1 to sha1.
- * Return a pointer to the refname within the line (null-terminated),
- * or NULL if there was a problem.
- */
-static const char *parse_ref_line(struct strbuf *line, struct object_id *oid)
-{
-       const char *ref;
-
-       if (parse_oid_hex(line->buf, oid, &ref) < 0)
-               return NULL;
-       if (!isspace(*ref++))
-               return NULL;
-
-       if (isspace(*ref))
-               return NULL;
-
-       if (line->buf[line->len - 1] != '\n')
-               return NULL;
-       line->buf[--line->len] = 0;
-
-       return ref;
-}
-
-/*
- * Read from `packed_refs_file` into a newly-allocated
- * `packed_ref_cache` and return it. The return value will already
- * have its reference count incremented.
- *
- * A comment line of the form "# pack-refs with: " may contain zero or
- * more traits. We interpret the traits as follows:
- *
- *   No traits:
- *
- *      Probably no references are peeled. But if the file contains a
- *      peeled value for a reference, we will use it.
- *
- *   peeled:
- *
- *      References under "refs/tags/", if they *can* be peeled, *are*
- *      peeled in this file. References outside of "refs/tags/" are
- *      probably not peeled even if they could have been, but if we find
- *      a peeled value for such a reference we will use it.
- *
- *   fully-peeled:
- *
- *      All references in the file that can be peeled are peeled.
- *      Inversely (and this is more important), any references in the
- *      file for which no peeled value is recorded is not peelable. This
- *      trait should typically be written alongside "peeled" for
- *      compatibility with older clients, but we do not require it
- *      (i.e., "peeled" is a no-op if "fully-peeled" is set).
- */
-static struct packed_ref_cache *read_packed_refs(const char *packed_refs_file)
-{
-       FILE *f;
-       struct packed_ref_cache *packed_refs = xcalloc(1, sizeof(*packed_refs));
-       struct ref_entry *last = NULL;
-       struct strbuf line = STRBUF_INIT;
-       enum { PEELED_NONE, PEELED_TAGS, PEELED_FULLY } peeled = PEELED_NONE;
-       struct ref_dir *dir;
-
-       acquire_packed_ref_cache(packed_refs);
-       packed_refs->cache = create_ref_cache(NULL, NULL);
-       packed_refs->cache->root->flag &= ~REF_INCOMPLETE;
-
-       f = fopen(packed_refs_file, "r");
-       if (!f) {
-               if (errno == ENOENT) {
-                       /*
-                        * This is OK; it just means that no
-                        * "packed-refs" file has been written yet,
-                        * which is equivalent to it being empty.
-                        */
-                       return packed_refs;
-               } else {
-                       die_errno("couldn't read %s", packed_refs_file);
-               }
-       }
-
-       stat_validity_update(&packed_refs->validity, fileno(f));
-
-       dir = get_ref_dir(packed_refs->cache->root);
-       while (strbuf_getwholeline(&line, f, '\n') != EOF) {
-               struct object_id oid;
-               const char *refname;
-               const char *traits;
-
-               if (skip_prefix(line.buf, "# pack-refs with:", &traits)) {
-                       if (strstr(traits, " fully-peeled "))
-                               peeled = PEELED_FULLY;
-                       else if (strstr(traits, " peeled "))
-                               peeled = PEELED_TAGS;
-                       /* perhaps other traits later as well */
-                       continue;
-               }
-
-               refname = parse_ref_line(&line, &oid);
-               if (refname) {
-                       int flag = REF_ISPACKED;
-
-                       if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
-                               if (!refname_is_safe(refname))
-                                       die("packed refname is dangerous: %s", refname);
-                               oidclr(&oid);
-                               flag |= REF_BAD_NAME | REF_ISBROKEN;
-                       }
-                       last = create_ref_entry(refname, &oid, flag);
-                       if (peeled == PEELED_FULLY ||
-                           (peeled == PEELED_TAGS && starts_with(refname, "refs/tags/")))
-                               last->flag |= REF_KNOWS_PEELED;
-                       add_ref_entry(dir, last);
-                       continue;
-               }
-               if (last &&
-                   line.buf[0] == '^' &&
-                   line.len == PEELED_LINE_LENGTH &&
-                   line.buf[PEELED_LINE_LENGTH - 1] == '\n' &&
-                   !get_oid_hex(line.buf + 1, &oid)) {
-                       oidcpy(&last->u.value.peeled, &oid);
-                       /*
-                        * Regardless of what the file header said,
-                        * we definitely know the value of *this*
-                        * reference:
-                        */
-                       last->flag |= REF_KNOWS_PEELED;
-               }
-       }
-
-       fclose(f);
-       strbuf_release(&line);
-
-       return packed_refs;
-}
-
-static const char *files_packed_refs_path(struct files_ref_store *refs)
-{
-       return refs->packed_refs_path;
-}
-
 static void files_reflog_path(struct files_ref_store *refs,
                              struct strbuf *sb,
                              const char *refname)
 {
-       if (!refname) {
-               /*
-                * FIXME: of course this is wrong in multi worktree
-                * setting. To be fixed real soon.
-                */
-               strbuf_addf(sb, "%s/logs", refs->gitcommondir);
-               return;
-       }
-
        switch (ref_type(refname)) {
        case REF_TYPE_PER_WORKTREE:
        case REF_TYPE_PSEUDOREF:
@@ -347,7 +162,7 @@ static void files_reflog_path(struct files_ref_store *refs,
                strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
                break;
        default:
-               die("BUG: unknown ref type %d of ref %s",
+               BUG("unknown ref type %d of ref %s",
                    ref_type(refname), refname);
        }
 }
@@ -365,75 +180,11 @@ static void files_ref_path(struct files_ref_store *refs,
                strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
                break;
        default:
-               die("BUG: unknown ref type %d of ref %s",
+               BUG("unknown ref type %d of ref %s",
                    ref_type(refname), refname);
        }
 }
 
-/*
- * Check that the packed refs cache (if any) still reflects the
- * contents of the file. If not, clear the cache.
- */
-static void validate_packed_ref_cache(struct files_ref_store *refs)
-{
-       if (refs->packed &&
-           !stat_validity_check(&refs->packed->validity,
-                                files_packed_refs_path(refs)))
-               clear_packed_ref_cache(refs);
-}
-
-/*
- * Get the packed_ref_cache for the specified files_ref_store,
- * creating and populating it if it hasn't been read before or if the
- * file has been changed (according to its `validity` field) since it
- * was last read. On the other hand, if we hold the lock, then assume
- * that the file hasn't been changed out from under us, so skip the
- * extra `stat()` call in `stat_validity_check()`.
- */
-static struct packed_ref_cache *get_packed_ref_cache(struct files_ref_store *refs)
-{
-       const char *packed_refs_file = files_packed_refs_path(refs);
-
-       if (!is_lock_file_locked(&refs->packed_refs_lock))
-               validate_packed_ref_cache(refs);
-
-       if (!refs->packed)
-               refs->packed = read_packed_refs(packed_refs_file);
-
-       return refs->packed;
-}
-
-static struct ref_dir *get_packed_ref_dir(struct packed_ref_cache *packed_ref_cache)
-{
-       return get_ref_dir(packed_ref_cache->cache->root);
-}
-
-static struct ref_dir *get_packed_refs(struct files_ref_store *refs)
-{
-       return get_packed_ref_dir(get_packed_ref_cache(refs));
-}
-
-/*
- * Add a reference to the in-memory packed reference cache.  This may
- * only be called while the packed-refs file is locked (see
- * lock_packed_refs()).  To actually write the packed-refs file, call
- * commit_packed_refs().
- */
-static void add_packed_ref(struct files_ref_store *refs,
-                          const char *refname, const struct object_id *oid)
-{
-       struct packed_ref_cache *packed_ref_cache = get_packed_ref_cache(refs);
-
-       if (!is_lock_file_locked(&refs->packed_refs_lock))
-               die("BUG: packed refs not locked");
-
-       if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
-               die("Reference has invalid format: '%s'", refname);
-
-       add_ref_entry(get_packed_ref_dir(packed_ref_cache),
-                     create_ref_entry(refname, oid, REF_ISPACKED));
-}
-
 /*
  * Read the loose references from the namespace dirname into dir
  * (without recursing).  dirname must end with '/'.  dir must be the
@@ -485,13 +236,13 @@ static void loose_fill_ref_dir(struct ref_store *ref_store,
                        if (!refs_resolve_ref_unsafe(&refs->base,
                                                     refname.buf,
                                                     RESOLVE_REF_READING,
-                                                    oid.hash, &flag)) {
+                                                    &oid, &flag)) {
                                oidclr(&oid);
                                flag |= REF_ISBROKEN;
                        } else if (is_null_oid(&oid)) {
                                /*
                                 * It is so astronomically unlikely
-                                * that NULL_SHA1 is the SHA-1 of an
+                                * that null_oid is the OID of an
                                 * actual object that we consider its
                                 * appearance in a loose reference
                                 * file to be repo corruption
@@ -556,41 +307,8 @@ static struct ref_cache *get_loose_ref_cache(struct files_ref_store *refs)
        return refs->loose;
 }
 
-/*
- * 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(struct files_ref_store *refs,
-                                       const char *refname)
-{
-       return find_ref_entry(get_packed_refs(refs), refname);
-}
-
-/*
- * A loose ref file doesn't exist; check for a packed ref.
- */
-static int resolve_packed_ref(struct files_ref_store *refs,
-                             const char *refname,
-                             unsigned char *sha1, unsigned int *flags)
-{
-       struct ref_entry *entry;
-
-       /*
-        * The loose reference file does not exist; check for a packed
-        * reference.
-        */
-       entry = get_packed_ref(refs, refname);
-       if (entry) {
-               hashcpy(sha1, entry->u.value.oid.hash);
-               *flags |= REF_ISPACKED;
-               return 0;
-       }
-       /* refname is not a packed reference. */
-       return -1;
-}
-
 static int files_read_raw_ref(struct ref_store *ref_store,
-                             const char *refname, unsigned char *sha1,
+                             const char *refname, struct object_id *oid,
                              struct strbuf *referent, unsigned int *type)
 {
        struct files_ref_store *refs =
@@ -599,6 +317,7 @@ static int files_read_raw_ref(struct ref_store *ref_store,
        struct strbuf sb_path = STRBUF_INIT;
        const char *path;
        const char *buf;
+       const char *p;
        struct stat st;
        int fd;
        int ret = -1;
@@ -632,7 +351,8 @@ static int files_read_raw_ref(struct ref_store *ref_store,
        if (lstat(path, &st) < 0) {
                if (errno != ENOENT)
                        goto out;
-               if (resolve_packed_ref(refs, refname, sha1, type)) {
+               if (refs_read_raw_ref(refs->packed_ref_store, refname,
+                                     oid, referent, type)) {
                        errno = ENOENT;
                        goto out;
                }
@@ -671,7 +391,8 @@ static int files_read_raw_ref(struct ref_store *ref_store,
                 * ref is supposed to be, there could still be a
                 * packed ref:
                 */
-               if (resolve_packed_ref(refs, refname, sha1, type)) {
+               if (refs_read_raw_ref(refs->packed_ref_store, refname,
+                                     oid, referent, type)) {
                        errno = EISDIR;
                        goto out;
                }
@@ -717,8 +438,8 @@ static int files_read_raw_ref(struct ref_store *ref_store,
         * Please note that FETCH_HEAD has additional
         * data after the sha.
         */
-       if (get_sha1_hex(buf, sha1) ||
-           (buf[40] != '\0' && !isspace(buf[40]))) {
+       if (parse_oid_hex(buf, oid, &p) ||
+           (*p != '\0' && !isspace(*p))) {
                *type |= REF_ISBROKEN;
                errno = EINVAL;
                goto out;
@@ -736,9 +457,7 @@ static int files_read_raw_ref(struct ref_store *ref_store,
 
 static void unlock_ref(struct ref_lock *lock)
 {
-       /* Do not free lock->lk -- atexit() still looks at them */
-       if (lock->lk)
-               rollback_lock_file(lock->lk);
+       rollback_lock_file(&lock->lk);
        free(lock->ref_name);
        free(lock);
 }
@@ -756,7 +475,7 @@ static void unlock_ref(struct ref_lock *lock)
  * are passed to refs_verify_refname_available() for this check.
  *
  * If mustexist is not set and the reference is not found or is
- * broken, lock the reference anyway but clear sha1.
+ * broken, lock the reference anyway but clear old_oid.
  *
  * Return 0 on success. On failure, write an error message to err and
  * return TRANSACTION_NAME_CONFLICT or TRANSACTION_GENERIC_ERROR.
@@ -852,10 +571,9 @@ static int lock_raw_ref(struct files_ref_store *refs,
                goto error_return;
        }
 
-       if (!lock->lk)
-               lock->lk = xcalloc(1, sizeof(struct lock_file));
-
-       if (hold_lock_file_for_update(lock->lk, ref_file.buf, LOCK_NO_DEREF) < 0) {
+       if (hold_lock_file_for_update_timeout(
+                           &lock->lk, ref_file.buf, LOCK_NO_DEREF,
+                           get_files_ref_lock_timeout_ms()) < 0) {
                if (errno == ENOENT && --attempts_remaining > 0) {
                        /*
                         * Maybe somebody just deleted one of the
@@ -875,7 +593,7 @@ static int lock_raw_ref(struct files_ref_store *refs,
         */
 
        if (files_read_raw_ref(&refs->base, refname,
-                              lock->old_oid.hash, referent, type)) {
+                              &lock->old_oid, referent, type)) {
                if (errno == ENOENT) {
                        if (mustexist) {
                                /* Garden variety missing reference. */
@@ -950,11 +668,11 @@ static int lock_raw_ref(struct files_ref_store *refs,
 
                /*
                 * If the ref did not exist and we are creating it,
-                * make sure there is no existing ref that conflicts
-                * with refname:
+                * make sure there is no existing packed ref that
+                * conflicts with refname:
                 */
                if (refs_verify_refname_available(
-                                   &refs->base, refname,
+                                   refs->packed_ref_store, refname,
                                    extras, skip, err))
                        goto error_return;
        }
@@ -971,53 +689,9 @@ static int lock_raw_ref(struct files_ref_store *refs,
        return ret;
 }
 
-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, REF_STORE_READ | REF_STORE_ODB,
-                              "peel_ref");
-       int flag;
-       unsigned char base[20];
-
-       if (current_ref_iter && current_ref_iter->refname == refname) {
-               struct object_id peeled;
-
-               if (ref_iterator_peel(current_ref_iter, &peeled))
-                       return -1;
-               hashcpy(sha1, peeled.hash);
-               return 0;
-       }
-
-       if (refs_read_ref_full(ref_store, refname,
-                              RESOLVE_REF_READING, base, &flag))
-               return -1;
-
-       /*
-        * If the reference is packed, read its ref_entry from the
-        * cache in the hope that we already know its peeled value.
-        * We only try this optimization on packed references because
-        * (a) forcing the filling of the loose reference cache could
-        * be expensive and (b) loose references anyway usually do not
-        * have REF_KNOWS_PEELED.
-        */
-       if (flag & REF_ISPACKED) {
-               struct ref_entry *r = get_packed_ref(refs, refname);
-               if (r) {
-                       if (peel_entry(r, 0))
-                               return -1;
-                       hashcpy(sha1, r->u.value.peeled.hash);
-                       return 0;
-               }
-       }
-
-       return peel_object(base, sha1);
-}
-
 struct files_ref_iterator {
        struct ref_iterator base;
 
-       struct packed_ref_cache *packed_ref_cache;
        struct ref_iterator *iter0;
        unsigned int flags;
 };
@@ -1070,7 +744,6 @@ static int files_ref_iterator_abort(struct ref_iterator *ref_iterator)
        if (iter->iter0)
                ok = ref_iterator_abort(iter->iter0);
 
-       release_packed_ref_cache(iter->packed_ref_cache);
        base_ref_iterator_free(ref_iterator);
        return ok;
 }
@@ -1086,7 +759,7 @@ static struct ref_iterator *files_ref_iterator_begin(
                const char *prefix, unsigned int flags)
 {
        struct files_ref_store *refs;
-       struct ref_iterator *loose_iter, *packed_iter;
+       struct ref_iterator *loose_iter, *packed_iter, *overlay_iter;
        struct files_ref_iterator *iter;
        struct ref_iterator *ref_iterator;
        unsigned int required_flags = REF_STORE_READ;
@@ -1096,10 +769,6 @@ static struct ref_iterator *files_ref_iterator_begin(
 
        refs = files_downcast(ref_store, required_flags, "ref_iterator_begin");
 
-       iter = xcalloc(1, sizeof(*iter));
-       ref_iterator = &iter->base;
-       base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable);
-
        /*
         * We must make sure that all loose refs are read before
         * accessing the packed-refs file; this avoids a race
@@ -1112,41 +781,57 @@ static struct ref_iterator *files_ref_iterator_begin(
         * (If they've already been read, that's OK; we only need to
         * guarantee that they're read before the packed refs, not
         * *how much* before.) After that, we call
-        * get_packed_ref_cache(), which internally checks whether the
-        * packed-ref cache is up to date with what is on disk, and
-        * re-reads it if not.
+        * packed_ref_iterator_begin(), which internally checks
+        * whether the packed-ref cache is up to date with what is on
+        * disk, and re-reads it if not.
         */
 
        loose_iter = cache_ref_iterator_begin(get_loose_ref_cache(refs),
                                              prefix, 1);
 
-       iter->packed_ref_cache = get_packed_ref_cache(refs);
-       acquire_packed_ref_cache(iter->packed_ref_cache);
-       packed_iter = cache_ref_iterator_begin(iter->packed_ref_cache->cache,
-                                              prefix, 0);
+       /*
+        * The packed-refs file might contain broken references, for
+        * example an old version of a reference that points at an
+        * object that has since been garbage-collected. This is OK as
+        * long as there is a corresponding loose reference that
+        * overrides it, and we don't want to emit an error message in
+        * this case. So ask the packed_ref_store for all of its
+        * references, and (if needed) do our own check for broken
+        * ones in files_ref_iterator_advance(), after we have merged
+        * the packed and loose references.
+        */
+       packed_iter = refs_ref_iterator_begin(
+                       refs->packed_ref_store, prefix, 0,
+                       DO_FOR_EACH_INCLUDE_BROKEN);
 
-       iter->iter0 = overlay_ref_iterator_begin(loose_iter, packed_iter);
+       overlay_iter = overlay_ref_iterator_begin(loose_iter, packed_iter);
+
+       iter = xcalloc(1, sizeof(*iter));
+       ref_iterator = &iter->base;
+       base_ref_iterator_init(ref_iterator, &files_ref_iterator_vtable,
+                              overlay_iter->ordered);
+       iter->iter0 = overlay_iter;
        iter->flags = flags;
 
        return ref_iterator;
 }
 
 /*
- * Verify that the reference locked by lock has the value old_sha1.
- * Fail if the reference doesn't exist and mustexist is set. Return 0
- * on success. On error, write an error message to err, set errno, and
- * return a negative value.
+ * Verify that the reference locked by lock has the value old_oid
+ * (unless it is NULL).  Fail if the reference doesn't exist and
+ * mustexist is set. Return 0 on success. On error, write an error
+ * message to err, set errno, and return a negative value.
  */
 static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
-                      const unsigned char *old_sha1, int mustexist,
+                      const struct object_id *old_oid, int mustexist,
                       struct strbuf *err)
 {
        assert(err);
 
        if (refs_read_ref_full(ref_store, lock->ref_name,
                               mustexist ? RESOLVE_REF_READING : 0,
-                              lock->old_oid.hash, NULL)) {
-               if (old_sha1) {
+                              &lock->old_oid, NULL)) {
+               if (old_oid) {
                        int save_errno = errno;
                        strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
                        errno = save_errno;
@@ -1156,11 +841,11 @@ static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
                        return 0;
                }
        }
-       if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
+       if (old_oid && oidcmp(&lock->old_oid, old_oid)) {
                strbuf_addf(err, "ref '%s' is at %s but expected %s",
                            lock->ref_name,
                            oid_to_hex(&lock->old_oid),
-                           sha1_to_hex(old_sha1));
+                           oid_to_hex(old_oid));
                errno = EBUSY;
                return -1;
        }
@@ -1181,29 +866,31 @@ 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;
+       return hold_lock_file_for_update_timeout(
+                       lk, path, LOCK_NO_DEREF,
+                       get_files_ref_lock_timeout_ms()) < 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(struct files_ref_store *refs,
-                                           const char *refname,
-                                           const unsigned char *old_sha1,
-                                           const struct string_list *extras,
-                                           const struct string_list *skip,
-                                           unsigned int flags, int *type,
-                                           struct strbuf *err)
+static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
+                                          const char *refname,
+                                          const struct object_id *old_oid,
+                                          const struct string_list *extras,
+                                          const struct string_list *skip,
+                                          unsigned int flags, int *type,
+                                          struct strbuf *err)
 {
        struct strbuf ref_file = STRBUF_INIT;
        struct ref_lock *lock;
        int last_errno = 0;
-       int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
+       int mustexist = (old_oid && !is_null_oid(old_oid));
        int resolve_flags = RESOLVE_REF_NO_RECURSE;
        int resolved;
 
-       files_assert_main_repository(refs, "lock_ref_sha1_basic");
+       files_assert_main_repository(refs, "lock_ref_oid_basic");
        assert(err);
 
        lock = xcalloc(1, sizeof(struct ref_lock));
@@ -1216,7 +903,7 @@ static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
        files_ref_path(refs, &ref_file, refname);
        resolved = !!refs_resolve_ref_unsafe(&refs->base,
                                             refname, resolve_flags,
-                                            lock->old_oid.hash, type);
+                                            &lock->old_oid, type);
        if (!resolved && errno == EISDIR) {
                /*
                 * we are trying to lock foo but we used to
@@ -1235,7 +922,7 @@ static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
                }
                resolved = !!refs_resolve_ref_unsafe(&refs->base,
                                                     refname, resolve_flags,
-                                                    lock->old_oid.hash, type);
+                                                    &lock->old_oid, type);
        }
        if (!resolved) {
                last_errno = errno;
@@ -1255,23 +942,21 @@ static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
         * our refname.
         */
        if (is_null_oid(&lock->old_oid) &&
-           refs_verify_refname_available(&refs->base, refname,
+           refs_verify_refname_available(refs->packed_ref_store, refname,
                                          extras, skip, err)) {
                last_errno = ENOTDIR;
                goto error_return;
        }
 
-       lock->lk = xcalloc(1, sizeof(struct lock_file));
-
        lock->ref_name = xstrdup(refname);
 
-       if (raceproof_create_file(ref_file.buf, create_reflock, lock->lk)) {
+       if (raceproof_create_file(ref_file.buf, create_reflock, &lock->lk)) {
                last_errno = errno;
                unable_to_lock_message(ref_file.buf, errno, err);
                goto error_return;
        }
 
-       if (verify_lock(&refs->base, lock, old_sha1, mustexist, err)) {
+       if (verify_lock(&refs->base, lock, old_oid, mustexist, err)) {
                last_errno = errno;
                goto error_return;
        }
@@ -1287,127 +972,9 @@ static struct ref_lock *lock_ref_sha1_basic(struct files_ref_store *refs,
        return lock;
 }
 
-/*
- * Write an entry to the packed-refs file for the specified refname.
- * If peeled is non-NULL, write it as the entry's peeled value.
- */
-static void write_packed_entry(FILE *fh, const char *refname,
-                              const unsigned char *sha1,
-                              const unsigned char *peeled)
-{
-       fprintf_or_die(fh, "%s %s\n", sha1_to_hex(sha1), refname);
-       if (peeled)
-               fprintf_or_die(fh, "^%s\n", sha1_to_hex(peeled));
-}
-
-/*
- * Lock the packed-refs file for writing. Flags is passed to
- * hold_lock_file_for_update(). Return 0 on success. On errors, set
- * errno appropriately and return a nonzero value.
- */
-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;
-
-       files_assert_main_repository(refs, "lock_packed_refs");
-
-       if (!timeout_configured) {
-               git_config_get_int("core.packedrefstimeout", &timeout_value);
-               timeout_configured = 1;
-       }
-
-       if (hold_lock_file_for_update_timeout(
-                           &refs->packed_refs_lock, files_packed_refs_path(refs),
-                           flags, timeout_value) < 0)
-               return -1;
-
-       /*
-        * Now that we hold the `packed-refs` lock, make sure that our
-        * cache matches the current version of the file. Normally
-        * `get_packed_ref_cache()` does that for us, but that
-        * function assumes that when the file is locked, any existing
-        * cache is still valid. We've just locked the file, but it
-        * might have changed the moment *before* we locked it.
-        */
-       validate_packed_ref_cache(refs);
-
-       packed_ref_cache = get_packed_ref_cache(refs);
-       /* Increment the reference count to prevent it from being freed: */
-       acquire_packed_ref_cache(packed_ref_cache);
-       return 0;
-}
-
-/*
- * Write the current version of the packed refs cache from memory to
- * disk. The packed-refs file must already be locked for writing (see
- * lock_packed_refs()). Return zero on success. On errors, set errno
- * and return a nonzero value
- */
-static int commit_packed_refs(struct files_ref_store *refs)
-{
-       struct packed_ref_cache *packed_ref_cache =
-               get_packed_ref_cache(refs);
-       int ok, error = 0;
-       int save_errno = 0;
-       FILE *out;
-       struct ref_iterator *iter;
-
-       files_assert_main_repository(refs, "commit_packed_refs");
-
-       if (!is_lock_file_locked(&refs->packed_refs_lock))
-               die("BUG: packed-refs not locked");
-
-       out = fdopen_lock_file(&refs->packed_refs_lock, "w");
-       if (!out)
-               die_errno("unable to fdopen packed-refs descriptor");
-
-       fprintf_or_die(out, "%s", PACKED_REFS_HEADER);
-
-       iter = cache_ref_iterator_begin(packed_ref_cache->cache, NULL, 0);
-       while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
-               struct object_id peeled;
-               int peel_error = ref_iterator_peel(iter, &peeled);
-
-               write_packed_entry(out, iter->refname, iter->oid->hash,
-                                  peel_error ? NULL : peeled.hash);
-       }
-
-       if (ok != ITER_DONE)
-               die("error while iterating over references");
-
-       if (commit_lock_file(&refs->packed_refs_lock)) {
-               save_errno = errno;
-               error = -1;
-       }
-       release_packed_ref_cache(packed_ref_cache);
-       errno = save_errno;
-       return error;
-}
-
-/*
- * Rollback the lockfile for the packed-refs file, and discard the
- * 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(struct files_ref_store *refs)
-{
-       struct packed_ref_cache *packed_ref_cache =
-               get_packed_ref_cache(refs);
-
-       files_assert_main_repository(refs, "rollback_packed_refs");
-
-       if (!is_lock_file_locked(&refs->packed_refs_lock))
-               die("BUG: packed-refs not locked");
-       rollback_lock_file(&refs->packed_refs_lock);
-       release_packed_ref_cache(packed_ref_cache);
-       clear_packed_ref_cache(refs);
-}
-
 struct ref_to_prune {
        struct ref_to_prune *next;
-       unsigned char sha1[20];
+       struct object_id oid;
        char name[FLEX_ARRAY];
 };
 
@@ -1469,29 +1036,42 @@ static void prune_ref(struct files_ref_store *refs, struct ref_to_prune *r)
 {
        struct ref_transaction *transaction;
        struct strbuf err = STRBUF_INIT;
+       int ret = -1;
 
        if (check_refname_format(r->name, 0))
                return;
 
        transaction = ref_store_transaction_begin(&refs->base, &err);
-       if (!transaction ||
-           ref_transaction_delete(transaction, r->name, r->sha1,
-                                  REF_ISPRUNING | REF_NODEREF, NULL, &err) ||
-           ref_transaction_commit(transaction, &err)) {
-               ref_transaction_free(transaction);
+       if (!transaction)
+               goto cleanup;
+       ref_transaction_add_update(
+                       transaction, r->name,
+                       REF_NO_DEREF | REF_HAVE_NEW | REF_HAVE_OLD | REF_IS_PRUNING,
+                       &null_oid, &r->oid, NULL);
+       if (ref_transaction_commit(transaction, &err))
+               goto cleanup;
+
+       ret = 0;
+
+cleanup:
+       if (ret)
                error("%s", err.buf);
-               strbuf_release(&err);
-               return;
-       }
-       ref_transaction_free(transaction);
        strbuf_release(&err);
+       ref_transaction_free(transaction);
+       return;
 }
 
-static void prune_refs(struct files_ref_store *refs, struct ref_to_prune *r)
+/*
+ * Prune the loose versions of the references in the linked list
+ * `*refs_to_prune`, freeing the entries in the list as we go.
+ */
+static void prune_refs(struct files_ref_store *refs, struct ref_to_prune **refs_to_prune)
 {
-       while (r) {
+       while (*refs_to_prune) {
+               struct ref_to_prune *r = *refs_to_prune;
+               *refs_to_prune = r->next;
                prune_ref(refs, r);
-               r = r->next;
+               free(r);
        }
 }
 
@@ -1527,12 +1107,16 @@ static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
                files_downcast(ref_store, REF_STORE_WRITE | REF_STORE_ODB,
                               "pack_refs");
        struct ref_iterator *iter;
-       struct ref_dir *packed_refs;
        int ok;
        struct ref_to_prune *refs_to_prune = NULL;
+       struct strbuf err = STRBUF_INIT;
+       struct ref_transaction *transaction;
+
+       transaction = ref_store_transaction_begin(refs->packed_ref_store, &err);
+       if (!transaction)
+               return -1;
 
-       lock_packed_refs(refs, LOCK_DIE_ON_ERROR);
-       packed_refs = get_packed_refs(refs);
+       packed_refs_lock(refs->packed_ref_store, LOCK_DIE_ON_ERROR, &err);
 
        iter = cache_ref_iterator_begin(get_loose_ref_cache(refs), NULL, 0);
        while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
@@ -1541,35 +1125,25 @@ static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
                 * in the packed ref cache. If the reference should be
                 * pruned, also add it to refs_to_prune.
                 */
-               struct ref_entry *packed_entry;
-
                if (!should_pack_ref(iter->refname, iter->oid, iter->flags,
                                     flags))
                        continue;
 
                /*
-                * Create an entry in the packed-refs cache equivalent
-                * to the one from the loose ref cache, except that
-                * we don't copy the peeled status, because we want it
-                * to be re-peeled.
+                * Add a reference creation for this reference to the
+                * packed-refs transaction:
                 */
-               packed_entry = find_ref_entry(packed_refs, iter->refname);
-               if (packed_entry) {
-                       /* Overwrite existing packed entry with info from loose entry */
-                       packed_entry->flag = REF_ISPACKED;
-                       oidcpy(&packed_entry->u.value.oid, iter->oid);
-               } else {
-                       packed_entry = create_ref_entry(iter->refname, iter->oid,
-                                                       REF_ISPACKED);
-                       add_ref_entry(packed_refs, packed_entry);
-               }
-               oidclr(&packed_entry->u.value.peeled);
+               if (ref_transaction_update(transaction, iter->refname,
+                                          iter->oid, NULL,
+                                          REF_NO_DEREF, NULL, &err))
+                       die("failure preparing to create packed reference %s: %s",
+                           iter->refname, err.buf);
 
                /* Schedule the loose reference for pruning if requested. */
                if ((flags & PACK_REFS_PRUNE)) {
                        struct ref_to_prune *n;
                        FLEX_ALLOC_STR(n, name, iter->refname);
-                       hashcpy(n->sha1, iter->oid->hash);
+                       oidcpy(&n->oid, iter->oid);
                        n->next = refs_to_prune;
                        refs_to_prune = n;
                }
@@ -1577,67 +1151,16 @@ static int files_pack_refs(struct ref_store *ref_store, unsigned int flags)
        if (ok != ITER_DONE)
                die("error while iterating over references");
 
-       if (commit_packed_refs(refs))
-               die_errno("unable to overwrite old ref-pack file");
-
-       prune_refs(refs, refs_to_prune);
-       return 0;
-}
-
-/*
- * Rewrite the packed-refs file, omitting any refs listed in
- * 'refnames'. On error, leave packed-refs unchanged, write an error
- * message to 'err', and return a nonzero value.
- *
- * The refs in 'refnames' needn't be sorted. `err` must not be NULL.
- */
-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;
-
-       files_assert_main_repository(refs, "repack_without_refs");
-       assert(err);
-
-       /* Look for a packed ref */
-       for_each_string_list_item(refname, refnames) {
-               if (get_packed_ref(refs, refname->string)) {
-                       needs_repacking = 1;
-                       break;
-               }
-       }
-
-       /* Avoid locking if we have nothing to do */
-       if (!needs_repacking)
-               return 0; /* no refname exists in packed refs */
+       if (ref_transaction_commit(transaction, &err))
+               die("unable to write new packed-refs: %s", err.buf);
 
-       if (lock_packed_refs(refs, 0)) {
-               unable_to_lock_message(files_packed_refs_path(refs), errno, err);
-               return -1;
-       }
-       packed = get_packed_refs(refs);
+       ref_transaction_free(transaction);
 
-       /* Remove refnames from the cache */
-       for_each_string_list_item(refname, refnames)
-               if (remove_entry_from_dir(packed, refname->string) != -1)
-                       removed = 1;
-       if (!removed) {
-               /*
-                * All packed entries disappeared while we were
-                * acquiring the lock.
-                */
-               rollback_packed_refs(refs);
-               return 0;
-       }
+       packed_refs_unlock(refs->packed_ref_store);
 
-       /* Write what remains */
-       ret = commit_packed_refs(refs);
-       if (ret)
-               strbuf_addf(err, "unable to overwrite old ref-pack file: %s",
-                           strerror(errno));
-       return ret;
+       prune_refs(refs, &refs_to_prune);
+       strbuf_release(&err);
+       return 0;
 }
 
 static int files_delete_refs(struct ref_store *ref_store, const char *msg,
@@ -1651,24 +1174,16 @@ static int files_delete_refs(struct ref_store *ref_store, const char *msg,
        if (!refnames->nr)
                return 0;
 
-       result = repack_without_refs(refs, refnames, &err);
-       if (result) {
-               /*
-                * If we failed to rewrite the packed-refs file, then
-                * it is unsafe to try to remove loose refs, because
-                * doing so might expose an obsolete packed value for
-                * a reference that might even point at an object that
-                * has been garbage collected.
-                */
-               if (refnames->nr == 1)
-                       error(_("could not delete reference %s: %s"),
-                             refnames->items[0].string, err.buf);
-               else
-                       error(_("could not delete references: %s"), err.buf);
+       if (packed_refs_lock(refs->packed_ref_store, 0, &err))
+               goto error;
 
-               goto out;
+       if (refs_delete_refs(refs->packed_ref_store, msg, refnames, flags)) {
+               packed_refs_unlock(refs->packed_ref_store);
+               goto error;
        }
 
+       packed_refs_unlock(refs->packed_ref_store);
+
        for (i = 0; i < refnames->nr; i++) {
                const char *refname = refnames->items[i].string;
 
@@ -1676,9 +1191,24 @@ static int files_delete_refs(struct ref_store *ref_store, const char *msg,
                        result |= error(_("could not remove reference %s"), refname);
        }
 
-out:
        strbuf_release(&err);
        return result;
+
+error:
+       /*
+        * If we failed to rewrite the packed-refs file, then it is
+        * unsafe to try to remove loose refs, because doing so might
+        * expose an obsolete packed value for a reference that might
+        * even point at an object that has been garbage collected.
+        */
+       if (refnames->nr == 1)
+               error(_("could not delete reference %s: %s"),
+                     refnames->items[0].string, err.buf);
+       else
+               error(_("could not delete references: %s"), err.buf);
+
+       strbuf_release(&err);
+       return -1;
 }
 
 /*
@@ -1748,9 +1278,9 @@ static int commit_ref_update(struct files_ref_store *refs,
                             const struct object_id *oid, const char *logmsg,
                             struct strbuf *err);
 
-static int files_rename_ref(struct ref_store *ref_store,
+static int files_copy_or_rename_ref(struct ref_store *ref_store,
                            const char *oldrefname, const char *newrefname,
-                           const char *logmsg)
+                           const char *logmsg, int copy)
 {
        struct files_ref_store *refs =
                files_downcast(ref_store, REF_STORE_WRITE, "rename_ref");
@@ -1776,14 +1306,18 @@ static int files_rename_ref(struct ref_store *ref_store,
 
        if (!refs_resolve_ref_unsafe(&refs->base, oldrefname,
                                     RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
-                               orig_oid.hash, &flag)) {
+                               &orig_oid, &flag)) {
                ret = error("refname %s not found", oldrefname);
                goto out;
        }
 
        if (flag & REF_ISSYMREF) {
-               ret = error("refname %s is a symbolic ref, renaming it is not supported",
-                           oldrefname);
+               if (copy)
+                       ret = error("refname %s is a symbolic ref, copying it is not supported",
+                                   oldrefname);
+               else
+                       ret = error("refname %s is a symbolic ref, renaming it is not supported",
+                                   oldrefname);
                goto out;
        }
        if (!refs_rename_ref_available(&refs->base, oldrefname, newrefname)) {
@@ -1791,14 +1325,20 @@ static int files_rename_ref(struct ref_store *ref_store,
                goto out;
        }
 
-       if (log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
+       if (!copy && log && rename(sb_oldref.buf, tmp_renamed_log.buf)) {
                ret = error("unable to move logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
                            oldrefname, strerror(errno));
                goto out;
        }
 
-       if (refs_delete_ref(&refs->base, logmsg, oldrefname,
-                           orig_oid.hash, REF_NODEREF)) {
+       if (copy && log && copy_file(tmp_renamed_log.buf, sb_oldref.buf, 0644)) {
+               ret = error("unable to copy logfile logs/%s to logs/"TMP_RENAMED_LOG": %s",
+                           oldrefname, strerror(errno));
+               goto out;
+       }
+
+       if (!copy && refs_delete_ref(&refs->base, logmsg, oldrefname,
+                           &orig_oid, REF_NO_DEREF)) {
                error("unable to delete old %s", oldrefname);
                goto rollback;
        }
@@ -1810,11 +1350,11 @@ static int files_rename_ref(struct ref_store *ref_store,
         * the safety anyway; we want to delete the reference whatever
         * its current value.
         */
-       if (!refs_read_ref_full(&refs->base, newrefname,
+       if (!copy && !refs_read_ref_full(&refs->base, newrefname,
                                RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
-                               oid.hash, NULL) &&
+                               &oid, NULL) &&
            refs_delete_ref(&refs->base, NULL, newrefname,
-                           NULL, REF_NODEREF)) {
+                           NULL, REF_NO_DEREF)) {
                if (errno == EISDIR) {
                        struct strbuf path = STRBUF_INIT;
                        int result;
@@ -1838,10 +1378,13 @@ static int files_rename_ref(struct ref_store *ref_store,
 
        logmoved = log;
 
-       lock = lock_ref_sha1_basic(refs, newrefname, NULL, NULL, NULL,
-                                  REF_NODEREF, NULL, &err);
+       lock = lock_ref_oid_basic(refs, newrefname, NULL, NULL, NULL,
+                                 REF_NO_DEREF, NULL, &err);
        if (!lock) {
-               error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
+               if (copy)
+                       error("unable to copy '%s' to '%s': %s", oldrefname, newrefname, err.buf);
+               else
+                       error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
                strbuf_release(&err);
                goto rollback;
        }
@@ -1858,8 +1401,8 @@ static int files_rename_ref(struct ref_store *ref_store,
        goto out;
 
  rollback:
-       lock = lock_ref_sha1_basic(refs, oldrefname, NULL, NULL, NULL,
-                                  REF_NODEREF, NULL, &err);
+       lock = lock_ref_oid_basic(refs, oldrefname, NULL, NULL, NULL,
+                                 REF_NO_DEREF, NULL, &err);
        if (!lock) {
                error("unable to lock %s for rollback: %s", oldrefname, err.buf);
                strbuf_release(&err);
@@ -1892,16 +1435,32 @@ static int files_rename_ref(struct ref_store *ref_store,
        return ret;
 }
 
-static int close_ref(struct ref_lock *lock)
+static int files_rename_ref(struct ref_store *ref_store,
+                           const char *oldrefname, const char *newrefname,
+                           const char *logmsg)
+{
+       return files_copy_or_rename_ref(ref_store, oldrefname,
+                                newrefname, logmsg, 0);
+}
+
+static int files_copy_ref(struct ref_store *ref_store,
+                           const char *oldrefname, const char *newrefname,
+                           const char *logmsg)
+{
+       return files_copy_or_rename_ref(ref_store, oldrefname,
+                                newrefname, logmsg, 1);
+}
+
+static int close_ref_gently(struct ref_lock *lock)
 {
-       if (close_lock_file(lock->lk))
+       if (close_lock_file_gently(&lock->lk))
                return -1;
        return 0;
 }
 
 static int commit_ref(struct ref_lock *lock)
 {
-       char *path = get_locked_file_path(lock->lk);
+       char *path = get_locked_file_path(&lock->lk);
        struct stat st;
 
        if (!lstat(path, &st) && S_ISDIR(st.st_mode)) {
@@ -1925,7 +1484,7 @@ static int commit_ref(struct ref_lock *lock)
                free(path);
        }
 
-       if (commit_lock_file(lock->lk))
+       if (commit_lock_file(&lock->lk))
                return -1;
        return 0;
 }
@@ -2023,26 +1582,17 @@ static int log_ref_write_fd(int fd, const struct object_id *old_oid,
                            const struct object_id *new_oid,
                            const char *committer, const char *msg)
 {
-       int msglen, written;
-       unsigned maxlen, len;
-       char *logrec;
-
-       msglen = msg ? strlen(msg) : 0;
-       maxlen = strlen(committer) + msglen + 100;
-       logrec = xmalloc(maxlen);
-       len = xsnprintf(logrec, maxlen, "%s %s %s\n",
-                       oid_to_hex(old_oid),
-                       oid_to_hex(new_oid),
-                       committer);
-       if (msglen)
-               len += copy_reflog_msg(logrec + len - 1, msg) - 1;
-
-       written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
-       free(logrec);
-       if (written < 0)
-               return -1;
+       struct strbuf sb = STRBUF_INIT;
+       int ret = 0;
 
-       return 0;
+       strbuf_addf(&sb, "%s %s %s", oid_to_hex(old_oid), oid_to_hex(new_oid), committer);
+       if (msg && *msg)
+               copy_reflog_msg(&sb, msg);
+       strbuf_addch(&sb, '\n');
+       if (write_in_full(fd, sb.buf, sb.len) < 0)
+               ret = -1;
+       strbuf_release(&sb);
+       return ret;
 }
 
 static int files_log_ref_write(struct files_ref_store *refs,
@@ -2091,9 +1641,8 @@ static int files_log_ref_write(struct files_ref_store *refs,
 }
 
 /*
- * Write sha1 into the open lockfile, then close the lockfile. On
- * errors, rollback the lockfile, fill in *err and
- * return -1.
+ * Write oid into the open lockfile, then close the lockfile. On
+ * errors, rollback the lockfile, fill in *err and return -1.
  */
 static int write_ref_to_lockfile(struct ref_lock *lock,
                                 const struct object_id *oid, struct strbuf *err)
@@ -2102,7 +1651,7 @@ static int write_ref_to_lockfile(struct ref_lock *lock,
        struct object *o;
        int fd;
 
-       o = parse_object(oid);
+       o = parse_object(the_repository, oid);
        if (!o) {
                strbuf_addf(err,
                            "trying to write ref '%s' with nonexistent object %s",
@@ -2117,12 +1666,12 @@ static int write_ref_to_lockfile(struct ref_lock *lock,
                unlock_ref(lock);
                return -1;
        }
-       fd = get_lock_file_fd(lock->lk);
-       if (write_in_full(fd, oid_to_hex(oid), GIT_SHA1_HEXSZ) < 0 ||
+       fd = get_lock_file_fd(&lock->lk);
+       if (write_in_full(fd, oid_to_hex(oid), the_hash_algo->hexsz) < 0 ||
            write_in_full(fd, &term, 1) < 0 ||
-           close_ref(lock) < 0) {
+           close_ref_gently(lock) < 0) {
                strbuf_addf(err,
-                           "couldn't write '%s'", get_lock_file_path(lock->lk));
+                           "couldn't write '%s'", get_lock_file_path(&lock->lk));
                unlock_ref(lock);
                return -1;
        }
@@ -2166,13 +1715,12 @@ static int commit_ref_update(struct files_ref_store *refs,
                 * check with HEAD only which should cover 99% of all usage
                 * scenarios (even 100% of the default ones).
                 */
-               struct object_id head_oid;
                int head_flag;
                const char *head_ref;
 
                head_ref = refs_resolve_ref_unsafe(&refs->base, "HEAD",
                                                   RESOLVE_REF_READING,
-                                                  head_oid.hash, &head_flag);
+                                                  NULL, &head_flag);
                if (head_ref && (head_flag & REF_ISSYMREF) &&
                    !strcmp(head_ref, lock->ref_name)) {
                        struct strbuf log_err = STRBUF_INIT;
@@ -2199,7 +1747,7 @@ static int create_ref_symlink(struct ref_lock *lock, const char *target)
 {
        int ret = -1;
 #ifndef NO_SYMLINK_HEAD
-       char *ref_path = get_locked_file_path(lock->lk);
+       char *ref_path = get_locked_file_path(&lock->lk);
        unlink(ref_path);
        ret = symlink(target, ref_path);
        free(ref_path);
@@ -2218,7 +1766,7 @@ static void update_symref_reflog(struct files_ref_store *refs,
        struct object_id new_oid;
        if (logmsg &&
            !refs_read_ref_full(&refs->base, target,
-                               RESOLVE_REF_READING, new_oid.hash, NULL) &&
+                               RESOLVE_REF_READING, &new_oid, NULL) &&
            files_log_ref_write(refs, refname, &lock->old_oid,
                                &new_oid, logmsg, 0, &err)) {
                error("%s", err.buf);
@@ -2235,14 +1783,14 @@ static int create_symref_locked(struct files_ref_store *refs,
                return 0;
        }
 
-       if (!fdopen_lock_file(lock->lk, "w"))
+       if (!fdopen_lock_file(&lock->lk, "w"))
                return error("unable to fdopen %s: %s",
-                            lock->lk->tempfile.filename.buf, strerror(errno));
+                            lock->lk.tempfile->filename.buf, strerror(errno));
 
        update_symref_reflog(refs, lock, refname, target, logmsg);
 
        /* no error check; commit_ref will check ferror */
-       fprintf(lock->lk->tempfile.fp, "ref: %s\n", target);
+       fprintf(lock->lk.tempfile->fp, "ref: %s\n", target);
        if (commit_ref(lock) < 0)
                return error("unable to write symref for %s: %s", refname,
                             strerror(errno));
@@ -2259,9 +1807,9 @@ static int files_create_symref(struct ref_store *ref_store,
        struct ref_lock *lock;
        int ret;
 
-       lock = lock_ref_sha1_basic(refs, refname, NULL,
-                                  NULL, NULL, REF_NODEREF, NULL,
-                                  &err);
+       lock = lock_ref_oid_basic(refs, refname, NULL,
+                                 NULL, NULL, REF_NO_DEREF, NULL,
+                                 &err);
        if (!lock) {
                error("%s", err.buf);
                strbuf_release(&err);
@@ -2449,7 +1997,7 @@ static int files_for_each_reflog_ent_reverse(struct ref_store *ref_store,
 
        }
        if (!ret && sb.len)
-               die("BUG: reverse reflog parser had leftover data");
+               BUG("reverse reflog parser had leftover data");
 
        fclose(logfp);
        strbuf_release(&sb);
@@ -2507,7 +2055,7 @@ static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
 
                if (refs_read_ref_full(iter->ref_store,
                                       diter->relative_path, 0,
-                                      iter->oid.hash, &flags)) {
+                                      &iter->oid, &flags)) {
                        error("bad ref for %s", diter->path.buf);
                        continue;
                }
@@ -2527,7 +2075,7 @@ static int files_reflog_iterator_advance(struct ref_iterator *ref_iterator)
 static int files_reflog_iterator_peel(struct ref_iterator *ref_iterator,
                                   struct object_id *peeled)
 {
-       die("BUG: ref_iterator_peel() called for reflog_iterator");
+       BUG("ref_iterator_peel() called for reflog_iterator");
 }
 
 static int files_reflog_iterator_abort(struct ref_iterator *ref_iterator)
@@ -2549,23 +2097,64 @@ static struct ref_iterator_vtable files_reflog_iterator_vtable = {
        files_reflog_iterator_abort
 };
 
-static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
+static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
+                                                 const char *gitdir)
 {
-       struct files_ref_store *refs =
-               files_downcast(ref_store, REF_STORE_READ,
-                              "reflog_iterator_begin");
        struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
        struct ref_iterator *ref_iterator = &iter->base;
        struct strbuf sb = STRBUF_INIT;
 
-       base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
-       files_reflog_path(refs, &sb, NULL);
+       base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
+       strbuf_addf(&sb, "%s/logs", gitdir);
        iter->dir_iterator = dir_iterator_begin(sb.buf);
        iter->ref_store = ref_store;
        strbuf_release(&sb);
+
        return ref_iterator;
 }
 
+static enum iterator_selection reflog_iterator_select(
+       struct ref_iterator *iter_worktree,
+       struct ref_iterator *iter_common,
+       void *cb_data)
+{
+       if (iter_worktree) {
+               /*
+                * We're a bit loose here. We probably should ignore
+                * common refs if they are accidentally added as
+                * per-worktree refs.
+                */
+               return ITER_SELECT_0;
+       } else if (iter_common) {
+               if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
+                       return ITER_SELECT_1;
+
+               /*
+                * The main ref store may contain main worktree's
+                * per-worktree refs, which should be ignored
+                */
+               return ITER_SKIP_1;
+       } else
+               return ITER_DONE;
+}
+
+static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
+{
+       struct files_ref_store *refs =
+               files_downcast(ref_store, REF_STORE_READ,
+                              "reflog_iterator_begin");
+
+       if (!strcmp(refs->gitdir, refs->gitcommondir)) {
+               return reflog_iterator_begin(ref_store, refs->gitcommondir);
+       } else {
+               return merge_ref_iterator_begin(
+                       0,
+                       reflog_iterator_begin(ref_store, refs->gitdir),
+                       reflog_iterator_begin(ref_store, refs->gitcommondir),
+                       reflog_iterator_select, refs);
+       }
+}
+
 /*
  * If update is a direct update of head_ref (the reference pointed to
  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.
@@ -2580,7 +2169,7 @@ static int split_head_update(struct ref_update *update,
        struct ref_update *new_update;
 
        if ((update->flags & REF_LOG_ONLY) ||
-           (update->flags & REF_ISPRUNING) ||
+           (update->flags & REF_IS_PRUNING) ||
            (update->flags & REF_UPDATE_VIA_HEAD))
                return 0;
 
@@ -2589,11 +2178,10 @@ static int split_head_update(struct ref_update *update,
 
        /*
         * First make sure that HEAD is not already in the
-        * transaction. This insertion is O(N) in the transaction
+        * transaction. This check is O(lg N) in the transaction
         * size, but it happens at most once per transaction.
         */
-       item = string_list_insert(affected_refnames, "HEAD");
-       if (item->util) {
+       if (string_list_has_string(affected_refnames, "HEAD")) {
                /* An entry already existed */
                strbuf_addf(err,
                            "multiple updates for 'HEAD' (including one "
@@ -2604,10 +2192,18 @@ static int split_head_update(struct ref_update *update,
 
        new_update = ref_transaction_add_update(
                        transaction, "HEAD",
-                       update->flags | REF_LOG_ONLY | REF_NODEREF,
-                       update->new_oid.hash, update->old_oid.hash,
+                       update->flags | REF_LOG_ONLY | REF_NO_DEREF,
+                       &update->new_oid, &update->old_oid,
                        update->msg);
 
+       /*
+        * Add "HEAD". This insertion is O(N) in the transaction
+        * size, but it happens at most once per transaction.
+        * Add new_update->refname instead of a literal "HEAD".
+        */
+       if (strcmp(new_update->refname, "HEAD"))
+               BUG("%s unexpectedly not 'HEAD'", new_update->refname);
+       item = string_list_insert(affected_refnames, new_update->refname);
        item->util = new_update;
 
        return 0;
@@ -2615,8 +2211,8 @@ static int split_head_update(struct ref_update *update,
 
 /*
  * update is for a symref that points at referent and doesn't have
- * REF_NODEREF set. Split it into two updates:
- * - The original update, but with REF_LOG_ONLY and REF_NODEREF set
+ * REF_NO_DEREF set. Split it into two updates:
+ * - The original update, but with REF_LOG_ONLY and REF_NO_DEREF set
  * - A new, separate update for the referent reference
  * Note that the new update will itself be subject to splitting when
  * the iteration gets to it.
@@ -2634,13 +2230,12 @@ static int split_symref_update(struct files_ref_store *refs,
 
        /*
         * First make sure that referent is not already in the
-        * transaction. This insertion is O(N) in the transaction
+        * transaction. This check is O(lg N) in the transaction
         * size, but it happens at most once per symref in a
         * transaction.
         */
-       item = string_list_insert(affected_refnames, referent);
-       if (item->util) {
-               /* An entry already existed */
+       if (string_list_has_string(affected_refnames, referent)) {
+               /* An entry already exists */
                strbuf_addf(err,
                            "multiple updates for '%s' (including one "
                            "via symref '%s') are not allowed",
@@ -2662,19 +2257,30 @@ static int split_symref_update(struct files_ref_store *refs,
 
        new_update = ref_transaction_add_update(
                        transaction, referent, new_flags,
-                       update->new_oid.hash, update->old_oid.hash,
+                       &update->new_oid, &update->old_oid,
                        update->msg);
 
        new_update->parent_update = update;
 
        /*
         * Change the symbolic ref update to log only. Also, it
-        * doesn't need to check its old SHA-1 value, as that will be
+        * doesn't need to check its old OID value, as that will be
         * done when new_update is processed.
         */
-       update->flags |= REF_LOG_ONLY | REF_NODEREF;
+       update->flags |= REF_LOG_ONLY | REF_NO_DEREF;
        update->flags &= ~REF_HAVE_OLD;
 
+       /*
+        * Add the referent. This insertion is O(N) in the transaction
+        * size, but it happens at most once per symref in a
+        * transaction. Make sure to add new_update->refname, which will
+        * be valid as long as affected_refnames is in use, and NOT
+        * referent, which might soon be freed by our caller.
+        */
+       item = string_list_insert(affected_refnames, new_update->refname);
+       if (item->util)
+               BUG("%s unexpectedly found in affected_refnames",
+                   new_update->refname);
        item->util = new_update;
 
        return 0;
@@ -2727,10 +2333,10 @@ static int check_old_oid(struct ref_update *update, struct object_id *oid,
  * Prepare for carrying out update:
  * - Lock the reference referred to by update.
  * - Read the reference under lock.
- * - Check that its old SHA-1 value (if specified) is correct, and in
+ * - Check that its old OID value (if specified) is correct, and in
  *   any case record it in update->lock->old_oid for later use when
  *   writing the reflog.
- * - If it is a symref update without REF_NODEREF, split it up into a
+ * - If it is a symref update without REF_NO_DEREF, split it up into a
  *   REF_LOG_ONLY update of the symref and add a separate update for
  *   the referent to transaction.
  * - If it is an update of head_ref, add a corresponding REF_LOG_ONLY
@@ -2746,7 +2352,7 @@ static int lock_ref_for_update(struct files_ref_store *refs,
        struct strbuf referent = STRBUF_INIT;
        int mustexist = (update->flags & REF_HAVE_OLD) &&
                !is_null_oid(&update->old_oid);
-       int ret;
+       int ret = 0;
        struct ref_lock *lock;
 
        files_assert_main_repository(refs, "lock_ref_for_update");
@@ -2758,7 +2364,7 @@ static int lock_ref_for_update(struct files_ref_store *refs,
                ret = split_head_update(update, transaction, head_ref,
                                        affected_refnames, err);
                if (ret)
-                       return ret;
+                       goto out;
        }
 
        ret = lock_raw_ref(refs, update->refname, mustexist,
@@ -2772,35 +2378,37 @@ static int lock_ref_for_update(struct files_ref_store *refs,
                strbuf_addf(err, "cannot lock ref '%s': %s",
                            original_update_refname(update), reason);
                free(reason);
-               return ret;
+               goto out;
        }
 
        update->backend_data = lock;
 
        if (update->type & REF_ISSYMREF) {
-               if (update->flags & REF_NODEREF) {
+               if (update->flags & REF_NO_DEREF) {
                        /*
                         * We won't be reading the referent as part of
                         * the transaction, so we have to read it here
-                        * to record and possibly check old_sha1:
+                        * to record and possibly check old_oid:
                         */
                        if (refs_read_ref_full(&refs->base,
                                               referent.buf, 0,
-                                              lock->old_oid.hash, NULL)) {
+                                              &lock->old_oid, NULL)) {
                                if (update->flags & REF_HAVE_OLD) {
                                        strbuf_addf(err, "cannot lock ref '%s': "
                                                    "error reading reference",
                                                    original_update_refname(update));
-                                       return -1;
+                                       ret = TRANSACTION_GENERIC_ERROR;
+                                       goto out;
                                }
                        } else if (check_old_oid(update, &lock->old_oid, err)) {
-                               return TRANSACTION_GENERIC_ERROR;
+                               ret = TRANSACTION_GENERIC_ERROR;
+                               goto out;
                        }
                } else {
                        /*
                         * Create a new update for the reference this
                         * symref is pointing at. Also, we will record
-                        * and verify old_sha1 for this update as part
+                        * and verify old_oid for this update as part
                         * of processing the split-off update, so we
                         * don't have to do it here.
                         */
@@ -2808,17 +2416,19 @@ static int lock_ref_for_update(struct files_ref_store *refs,
                                                  referent.buf, transaction,
                                                  affected_refnames, err);
                        if (ret)
-                               return ret;
+                               goto out;
                }
        } else {
                struct ref_update *parent_update;
 
-               if (check_old_oid(update, &lock->old_oid, err))
-                       return TRANSACTION_GENERIC_ERROR;
+               if (check_old_oid(update, &lock->old_oid, err)) {
+                       ret = TRANSACTION_GENERIC_ERROR;
+                       goto out;
+               }
 
                /*
                 * If this update is happening indirectly because of a
-                * symref update, record the old SHA-1 in the parent
+                * symref update, record the old OID in the parent
                 * update:
                 */
                for (parent_update = update->parent_update;
@@ -2851,7 +2461,8 @@ static int lock_ref_for_update(struct files_ref_store *refs,
                                    "cannot update ref '%s': %s",
                                    update->refname, write_err);
                        free(write_err);
-                       return TRANSACTION_GENERIC_ERROR;
+                       ret = TRANSACTION_GENERIC_ERROR;
+                       goto out;
                } else {
                        update->flags |= REF_NEEDS_COMMIT;
                }
@@ -2862,22 +2473,35 @@ static int lock_ref_for_update(struct files_ref_store *refs,
                 * the lockfile is still open. Close it to
                 * free up the file descriptor:
                 */
-               if (close_ref(lock)) {
+               if (close_ref_gently(lock)) {
                        strbuf_addf(err, "couldn't close '%s.lock'",
                                    update->refname);
-                       return TRANSACTION_GENERIC_ERROR;
+                       ret = TRANSACTION_GENERIC_ERROR;
+                       goto out;
                }
        }
-       return 0;
+
+out:
+       strbuf_release(&referent);
+       return ret;
 }
 
+struct files_transaction_backend_data {
+       struct ref_transaction *packed_transaction;
+       int packed_refs_locked;
+};
+
 /*
  * Unlock any references in `transaction` that are still locked, and
  * mark the transaction closed.
  */
-static void files_transaction_cleanup(struct ref_transaction *transaction)
+static void files_transaction_cleanup(struct files_ref_store *refs,
+                                     struct ref_transaction *transaction)
 {
        size_t i;
+       struct files_transaction_backend_data *backend_data =
+               transaction->backend_data;
+       struct strbuf err = STRBUF_INIT;
 
        for (i = 0; i < transaction->nr; i++) {
                struct ref_update *update = transaction->updates[i];
@@ -2889,6 +2513,17 @@ static void files_transaction_cleanup(struct ref_transaction *transaction)
                }
        }
 
+       if (backend_data->packed_transaction &&
+           ref_transaction_abort(backend_data->packed_transaction, &err)) {
+               error("error aborting transaction: %s", err.buf);
+               strbuf_release(&err);
+       }
+
+       if (backend_data->packed_refs_locked)
+               packed_refs_unlock(refs->packed_ref_store);
+
+       free(backend_data);
+
        transaction->state = REF_TRANSACTION_CLOSED;
 }
 
@@ -2904,25 +2539,34 @@ static int files_transaction_prepare(struct ref_store *ref_store,
        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
        char *head_ref = NULL;
        int head_type;
-       struct object_id head_oid;
+       struct files_transaction_backend_data *backend_data;
+       struct ref_transaction *packed_transaction = NULL;
 
        assert(err);
 
        if (!transaction->nr)
                goto cleanup;
 
+       backend_data = xcalloc(1, sizeof(*backend_data));
+       transaction->backend_data = backend_data;
+
        /*
         * Fail if a refname appears more than once in the
         * transaction. (If we end up splitting up any updates using
         * split_symref_update() or split_head_update(), those
         * functions will check that the new updates don't have the
-        * same refname as any existing ones.)
+        * same refname as any existing ones.) Also fail if any of the
+        * updates use REF_IS_PRUNING without REF_NO_DEREF.
         */
        for (i = 0; i < transaction->nr; i++) {
                struct ref_update *update = transaction->updates[i];
                struct string_list_item *item =
                        string_list_append(&affected_refnames, update->refname);
 
+               if ((update->flags & REF_IS_PRUNING) &&
+                   !(update->flags & REF_NO_DEREF))
+                       BUG("REF_IS_PRUNING set without REF_NO_DEREF");
+
                /*
                 * We store a pointer to update in item->util, but at
                 * the moment we never use the value of this field
@@ -2956,7 +2600,7 @@ static int files_transaction_prepare(struct ref_store *ref_store,
         */
        head_ref = refs_resolve_refdup(ref_store, "HEAD",
                                       RESOLVE_REF_NO_RECURSE,
-                                      head_oid.hash, &head_type);
+                                      NULL, &head_type);
 
        if (head_ref && !(head_type & REF_ISSYMREF)) {
                FREE_AND_NULL(head_ref);
@@ -2976,7 +2620,58 @@ static int files_transaction_prepare(struct ref_store *ref_store,
                ret = lock_ref_for_update(refs, update, transaction,
                                          head_ref, &affected_refnames, err);
                if (ret)
-                       break;
+                       goto cleanup;
+
+               if (update->flags & REF_DELETING &&
+                   !(update->flags & REF_LOG_ONLY) &&
+                   !(update->flags & REF_IS_PRUNING)) {
+                       /*
+                        * This reference has to be deleted from
+                        * packed-refs if it exists there.
+                        */
+                       if (!packed_transaction) {
+                               packed_transaction = ref_store_transaction_begin(
+                                               refs->packed_ref_store, err);
+                               if (!packed_transaction) {
+                                       ret = TRANSACTION_GENERIC_ERROR;
+                                       goto cleanup;
+                               }
+
+                               backend_data->packed_transaction =
+                                       packed_transaction;
+                       }
+
+                       ref_transaction_add_update(
+                                       packed_transaction, update->refname,
+                                       REF_HAVE_NEW | REF_NO_DEREF,
+                                       &update->new_oid, NULL,
+                                       NULL);
+               }
+       }
+
+       if (packed_transaction) {
+               if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
+                       ret = TRANSACTION_GENERIC_ERROR;
+                       goto cleanup;
+               }
+               backend_data->packed_refs_locked = 1;
+
+               if (is_packed_transaction_needed(refs->packed_ref_store,
+                                                packed_transaction)) {
+                       ret = ref_transaction_prepare(packed_transaction, err);
+               } else {
+                       /*
+                        * We can skip rewriting the `packed-refs`
+                        * file. But we do need to leave it locked, so
+                        * that somebody else doesn't pack a reference
+                        * that we are trying to delete.
+                        */
+                       if (ref_transaction_abort(packed_transaction, err)) {
+                               ret = TRANSACTION_GENERIC_ERROR;
+                               goto cleanup;
+                       }
+                       backend_data->packed_transaction = NULL;
+               }
        }
 
 cleanup:
@@ -2984,7 +2679,7 @@ static int files_transaction_prepare(struct ref_store *ref_store,
        string_list_clear(&affected_refnames, 0);
 
        if (ret)
-               files_transaction_cleanup(transaction);
+               files_transaction_cleanup(refs, transaction);
        else
                transaction->state = REF_TRANSACTION_PREPARED;
 
@@ -2999,9 +2694,10 @@ static int files_transaction_finish(struct ref_store *ref_store,
                files_downcast(ref_store, 0, "ref_transaction_finish");
        size_t i;
        int ret = 0;
-       struct string_list refs_to_delete = STRING_LIST_INIT_NODUP;
-       struct string_list_item *ref_to_delete;
        struct strbuf sb = STRBUF_INIT;
+       struct files_transaction_backend_data *backend_data;
+       struct ref_transaction *packed_transaction;
+
 
        assert(err);
 
@@ -3010,6 +2706,9 @@ static int files_transaction_finish(struct ref_store *ref_store,
                return 0;
        }
 
+       backend_data = transaction->backend_data;
+       packed_transaction = backend_data->packed_transaction;
+
        /* Perform updates first so live commits remain referenced */
        for (i = 0; i < transaction->nr; i++) {
                struct ref_update *update = transaction->updates[i];
@@ -3045,7 +2744,44 @@ static int files_transaction_finish(struct ref_store *ref_store,
                        }
                }
        }
-       /* Perform deletes now that updates are safely completed */
+
+       /*
+        * Now that updates are safely completed, we can perform
+        * deletes. First delete the reflogs of any references that
+        * will be deleted, since (in the unexpected event of an
+        * error) leaving a reference without a reflog is less bad
+        * than leaving a reflog without a reference (the latter is a
+        * mildly invalid repository state):
+        */
+       for (i = 0; i < transaction->nr; i++) {
+               struct ref_update *update = transaction->updates[i];
+               if (update->flags & REF_DELETING &&
+                   !(update->flags & REF_LOG_ONLY) &&
+                   !(update->flags & REF_IS_PRUNING)) {
+                       strbuf_reset(&sb);
+                       files_reflog_path(refs, &sb, update->refname);
+                       if (!unlink_or_warn(sb.buf))
+                               try_remove_empty_parents(refs, update->refname,
+                                                        REMOVE_EMPTY_PARENTS_REFLOG);
+               }
+       }
+
+       /*
+        * Perform deletes now that updates are safely completed.
+        *
+        * First delete any packed versions of the references, while
+        * retaining the packed-refs lock:
+        */
+       if (packed_transaction) {
+               ret = ref_transaction_commit(packed_transaction, err);
+               ref_transaction_free(packed_transaction);
+               packed_transaction = NULL;
+               backend_data->packed_transaction = NULL;
+               if (ret)
+                       goto cleanup;
+       }
+
+       /* Now delete the loose versions of the references: */
        for (i = 0; i < transaction->nr; i++) {
                struct ref_update *update = transaction->updates[i];
                struct ref_lock *lock = update->backend_data;
@@ -3063,31 +2799,13 @@ static int files_transaction_finish(struct ref_store *ref_store,
                                }
                                update->flags |= REF_DELETED_LOOSE;
                        }
-
-                       if (!(update->flags & REF_ISPRUNING))
-                               string_list_append(&refs_to_delete,
-                                                  lock->ref_name);
                }
        }
 
-       if (repack_without_refs(refs, &refs_to_delete, err)) {
-               ret = TRANSACTION_GENERIC_ERROR;
-               goto cleanup;
-       }
-
-       /* Delete the reflogs of any references that were deleted: */
-       for_each_string_list_item(ref_to_delete, &refs_to_delete) {
-               strbuf_reset(&sb);
-               files_reflog_path(refs, &sb, ref_to_delete->string);
-               if (!unlink_or_warn(sb.buf))
-                       try_remove_empty_parents(refs, ref_to_delete->string,
-                                                REMOVE_EMPTY_PARENTS_REFLOG);
-       }
-
        clear_loose_ref_cache(refs);
 
 cleanup:
-       files_transaction_cleanup(transaction);
+       files_transaction_cleanup(refs, transaction);
 
        for (i = 0; i < transaction->nr; i++) {
                struct ref_update *update = transaction->updates[i];
@@ -3105,7 +2823,6 @@ static int files_transaction_finish(struct ref_store *ref_store,
        }
 
        strbuf_release(&sb);
-       string_list_clear(&refs_to_delete, 0);
        return ret;
 }
 
@@ -3113,7 +2830,10 @@ static int files_transaction_abort(struct ref_store *ref_store,
                                   struct ref_transaction *transaction,
                                   struct strbuf *err)
 {
-       files_transaction_cleanup(transaction);
+       struct files_ref_store *refs =
+               files_downcast(ref_store, 0, "ref_transaction_abort");
+
+       files_transaction_cleanup(refs, transaction);
        return 0;
 }
 
@@ -3135,11 +2855,12 @@ static int files_initial_transaction_commit(struct ref_store *ref_store,
        size_t i;
        int ret = 0;
        struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
+       struct ref_transaction *packed_transaction = NULL;
 
        assert(err);
 
        if (transaction->state != REF_TRANSACTION_OPEN)
-               die("BUG: commit called for transaction that is not open");
+               BUG("commit called for transaction that is not open");
 
        /* Fail if a refname appears more than once in the transaction: */
        for (i = 0; i < transaction->nr; i++)
@@ -3165,46 +2886,50 @@ static int files_initial_transaction_commit(struct ref_store *ref_store,
         */
        if (refs_for_each_rawref(&refs->base, ref_present,
                                 &affected_refnames))
-               die("BUG: initial ref transaction called with existing refs");
+               BUG("initial ref transaction called with existing refs");
+
+       packed_transaction = ref_store_transaction_begin(refs->packed_ref_store, err);
+       if (!packed_transaction) {
+               ret = TRANSACTION_GENERIC_ERROR;
+               goto cleanup;
+       }
 
        for (i = 0; i < transaction->nr; i++) {
                struct ref_update *update = transaction->updates[i];
 
                if ((update->flags & REF_HAVE_OLD) &&
                    !is_null_oid(&update->old_oid))
-                       die("BUG: initial ref transaction with old_sha1 set");
+                       BUG("initial ref transaction with old_sha1 set");
                if (refs_verify_refname_available(&refs->base, update->refname,
                                                  &affected_refnames, NULL,
                                                  err)) {
                        ret = TRANSACTION_NAME_CONFLICT;
                        goto cleanup;
                }
+
+               /*
+                * Add a reference creation for this reference to the
+                * packed-refs transaction:
+                */
+               ref_transaction_add_update(packed_transaction, update->refname,
+                                          update->flags & ~REF_HAVE_OLD,
+                                          &update->new_oid, &update->old_oid,
+                                          NULL);
        }
 
-       if (lock_packed_refs(refs, 0)) {
-               strbuf_addf(err, "unable to lock packed-refs file: %s",
-                           strerror(errno));
+       if (packed_refs_lock(refs->packed_ref_store, 0, err)) {
                ret = TRANSACTION_GENERIC_ERROR;
                goto cleanup;
        }
 
-       for (i = 0; i < transaction->nr; i++) {
-               struct ref_update *update = transaction->updates[i];
-
-               if ((update->flags & REF_HAVE_NEW) &&
-                   !is_null_oid(&update->new_oid))
-                       add_packed_ref(refs, update->refname,
-                                      &update->new_oid);
-       }
-
-       if (commit_packed_refs(refs)) {
-               strbuf_addf(err, "unable to commit packed-refs file: %s",
-                           strerror(errno));
+       if (initial_ref_transaction_commit(packed_transaction, err)) {
                ret = TRANSACTION_GENERIC_ERROR;
-               goto cleanup;
        }
 
+       packed_refs_unlock(refs->packed_ref_store);
 cleanup:
+       if (packed_transaction)
+               ref_transaction_free(packed_transaction);
        transaction->state = REF_TRANSACTION_CLOSED;
        string_list_clear(&affected_refnames, 0);
        return ret;
@@ -3248,7 +2973,7 @@ static int expire_reflog_ent(struct object_id *ooid, struct object_id *noid,
 }
 
 static int files_reflog_expire(struct ref_store *ref_store,
-                              const char *refname, const unsigned char *sha1,
+                              const char *refname, const struct object_id *oid,
                               unsigned int flags,
                               reflog_expiry_prepare_fn prepare_fn,
                               reflog_expiry_should_prune_fn should_prune_fn,
@@ -3257,7 +2982,7 @@ static int files_reflog_expire(struct ref_store *ref_store,
 {
        struct files_ref_store *refs =
                files_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
-       static struct lock_file reflog_lock;
+       struct lock_file reflog_lock = LOCK_INIT;
        struct expire_reflog_cb cb;
        struct ref_lock *lock;
        struct strbuf log_file_sb = STRBUF_INIT;
@@ -3265,7 +2990,6 @@ static int files_reflog_expire(struct ref_store *ref_store,
        int status = 0;
        int type;
        struct strbuf err = STRBUF_INIT;
-       struct object_id oid;
 
        memset(&cb, 0, sizeof(cb));
        cb.flags = flags;
@@ -3277,9 +3001,9 @@ static int files_reflog_expire(struct ref_store *ref_store,
         * reference itself, plus we might need to update the
         * reference if --updateref was specified:
         */
-       lock = lock_ref_sha1_basic(refs, refname, sha1,
-                                  NULL, NULL, REF_NODEREF,
-                                  &type, &err);
+       lock = lock_ref_oid_basic(refs, refname, oid,
+                                 NULL, NULL, REF_NO_DEREF,
+                                 &type, &err);
        if (!lock) {
                error("cannot lock ref '%s': %s", refname, err.buf);
                strbuf_release(&err);
@@ -3315,9 +3039,7 @@ static int files_reflog_expire(struct ref_store *ref_store,
                }
        }
 
-       hashcpy(oid.hash, sha1);
-
-       (*prepare_fn)(refname, &oid, cb.policy_cb);
+       (*prepare_fn)(refname, oid, cb.policy_cb);
        refs_for_each_reflog_ent(ref_store, refname, expire_reflog_ent, &cb);
        (*cleanup_fn)(cb.policy_cb);
 
@@ -3333,16 +3055,17 @@ static int files_reflog_expire(struct ref_store *ref_store,
                        !(type & REF_ISSYMREF) &&
                        !is_null_oid(&cb.last_kept_oid);
 
-               if (close_lock_file(&reflog_lock)) {
+               if (close_lock_file_gently(&reflog_lock)) {
                        status |= error("couldn't write %s: %s", log_file,
                                        strerror(errno));
+                       rollback_lock_file(&reflog_lock);
                } else if (update &&
-                          (write_in_full(get_lock_file_fd(lock->lk),
-                               oid_to_hex(&cb.last_kept_oid), GIT_SHA1_HEXSZ) < 0 ||
-                           write_str_in_full(get_lock_file_fd(lock->lk), "\n") < 0 ||
-                           close_ref(lock) < 0)) {
+                          (write_in_full(get_lock_file_fd(&lock->lk),
+                               oid_to_hex(&cb.last_kept_oid), the_hash_algo->hexsz) < 0 ||
+                           write_str_in_full(get_lock_file_fd(&lock->lk), "\n") < 0 ||
+                           close_ref_gently(lock) < 0)) {
                        status |= error("couldn't write %s",
-                                       get_lock_file_path(lock->lk));
+                                       get_lock_file_path(&lock->lk));
                        rollback_lock_file(&reflog_lock);
                } else if (commit_lock_file(&reflog_lock)) {
                        status |= error("unable to write reflog '%s' (%s)",
@@ -3393,10 +3116,10 @@ struct ref_storage_be refs_be_files = {
        files_initial_transaction_commit,
 
        files_pack_refs,
-       files_peel_ref,
        files_create_symref,
        files_delete_refs,
        files_rename_ref,
+       files_copy_ref,
 
        files_ref_iterator_begin,
        files_read_raw_ref,