refs: pass gitdir to packed_ref_store_create

This is consistent with the calling convention for ref backend creation, and
avoids storing ".git/packed-refs" (the name of a regular file) in a variable called
ref_store::gitdir.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 90b6710..f1b6613 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -93,9 +93,8 @@ static struct ref_store *files_ref_store_create(struct repository *repo,
 
 	get_common_dir_noenv(&sb, gitdir);
 	refs->gitcommondir = strbuf_detach(&sb, NULL);
-	strbuf_addf(&sb, "%s/packed-refs", refs->gitcommondir);
-	refs->packed_ref_store = packed_ref_store_create(repo, sb.buf, flags);
-	strbuf_release(&sb);
+	refs->packed_ref_store =
+		packed_ref_store_create(repo, refs->gitcommondir, flags);
 
 	chdir_notify_reparent("files-backend $GIT_DIR", &refs->base.gitdir);
 	chdir_notify_reparent("files-backend $GIT_COMMONDIR",