#include "../lockfile.h"
 #include "../object.h"
 #include "../dir.h"
+#include "../chdir-notify.h"
 
 /*
  * This backend uses the following flags in `ref_update::flags` for
        struct object_id old_oid;
 };
 
-/*
- * Future: need to be in "struct repository"
- * when doing a full libification.
- */
 struct files_ref_store {
        struct ref_store base;
        unsigned int store_flags;
        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;
 }
 
        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);
 }
 
 /*
        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;
                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);
        }
 }
                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);
        }
 }
                        } 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
  * 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.
 }
 
 /*
- * 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)
 
        }
        if (!ret && sb.len)
-               die("BUG: reverse reflog parser had leftover data");
+               BUG("reverse reflog parser had leftover data");
 
        fclose(logfp);
        strbuf_release(&sb);
 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)
 
        /*
         * 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_NO_DEREF;
  * 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_NO_DEREF, split it up into a
                        /*
                         * 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,
                        /*
                         * 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.
                         */
 
                /*
                 * 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;
                        goto cleanup;
                }
                backend_data->packed_refs_locked = 1;
-               ret = ref_transaction_prepare(packed_transaction, err);
+
+               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:
        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++)
         */
        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) {
 
                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)) {
 
        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);
-       packed_refs_unlock(refs->packed_ref_store);
        transaction->state = REF_TRANSACTION_CLOSED;
        string_list_clear(&affected_refnames, 0);
        return ret;
 {
        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;