refs: move submodule code out of files-backend.c

files-backend is now initialized with a $GIT_DIR. Converting a submodule
path to where real submodule gitdir is located is done in get_ref_store().

This gives a slight performance improvement for submodules since we
don't convert submodule path to gitdir at every backend call like
before. We pay that once at ref-store creation.

More cleanup in files_downcast() and files_assert_main_repository()
follows shortly. It's separate to keep noises from this patch.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 5 deletions

diff --git a/refs.c b/refs.c
index 1f4c1a234..d72b48a43 100644
--- a/refs.c
+++ b/refs.c
@@ -9,6 +9,7 @@
 #include "refs/refs-internal.h"
 #include "object.h"
 #include "tag.h"
+#include "submodule.h"
 
 /*
  * List of all available backends
@@ -1413,9 +1414,9 @@ static struct ref_store *lookup_submodule_ref_store(const char *submodule)
 
 /*
  * Create, record, and return a ref_store instance for the specified
- * submodule (or the main repository if submodule is NULL).
+ * gitdir.
  */
-static struct ref_store *ref_store_init(const char *submodule)
+static struct ref_store *ref_store_init(const char *gitdir)
 {
 	const char *be_name = "files";
 	struct ref_storage_be *be = find_ref_storage_backend(be_name);
@@ -1424,7 +1425,7 @@ static struct ref_store *ref_store_init(const char *submodule)
 	if (!be)
 		die("BUG: reference backend %s is unknown", be_name);
 
-	refs = be->init(submodule);
+	refs = be->init(gitdir);
 	return refs;
 }
 
@@ -1433,7 +1434,7 @@ struct ref_store *get_main_ref_store(void)
 	if (main_ref_store)
 		return main_ref_store;
 
-	main_ref_store = ref_store_init(NULL);
+	main_ref_store = ref_store_init(get_git_dir());
 	return main_ref_store;
 }
 
@@ -1474,8 +1475,16 @@ struct ref_store *get_ref_store(const char *submodule)
 	if (!ret)
 		return NULL;
 
-	refs = ref_store_init(submodule);
+	ret = submodule_to_gitdir(&submodule_sb, submodule);
+	if (ret) {
+		strbuf_release(&submodule_sb);
+		return NULL;
+	}
+
+	refs = ref_store_init(submodule_sb.buf);
 	register_submodule_ref_store(refs, submodule);
+
+	strbuf_release(&submodule_sb);
 	return refs;
 }