Re: [PATCH v5 15/24] 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 <redacted>
---
 refs.c               | 20 ++++++++++++++------
 refs/files-backend.c | 24 ++----------------------
 refs/refs-internal.h |  9 ++++-----
 3 files changed, 20 insertions(+), 33 deletions(-)

diff --git a/refs.c b/refs.c
index 562834fc0..67acae60c 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;
 }
 

@@ -1435,7 +1436,7 @@ struct ref_store *get_main_ref_store(void)
 	if (main_ref_store)
 		return main_ref_store;
 
-	refs = ref_store_init(NULL);
+	refs = ref_store_init(get_git_dir());
 	if (refs) {
 		if (main_ref_store)
 			die("BUG: main_ref_store initialized twice");

@@ -1466,6 +1467,7 @@ struct ref_store *get_ref_store(const char *submodule)
 {
 	struct strbuf submodule_sb = STRBUF_INIT;
 	struct ref_store *refs;
+	int ret;
 
 	if (!submodule || !*submodule) {
 		return get_main_ref_store();

@@ -1476,8 +1478,14 @@ struct ref_store *get_ref_store(const char *submodule)
 		return refs;
 
 	strbuf_addstr(&submodule_sb, submodule);
-	if (is_nonbare_repository_dir(&submodule_sb))
-		refs = ref_store_init(submodule);
+	ret = is_nonbare_repository_dir(&submodule_sb);
+	strbuf_release(&submodule_sb);
+	if (!ret)
+		return refs;

+
+	ret = submodule_to_gitdir(&submodule_sb, submodule);
+	if (!ret)
+		refs = ref_store_init(submodule_sb.buf);
 	strbuf_release(&submodule_sb);
 
 	if (refs)

diff --git a/refs/files-backend.c b/refs/files-backend.c
index d80c27837..37443369b 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c

@@ -917,12 +917,6 @@ struct packed_ref_cache {
 struct files_ref_store {
 	struct ref_store base;
 
-	/*
-	 * The name of the submodule represented by this object, or
-	 * NULL if it represents the main repository's reference
-	 * store:
-	 */
-	const char *submodule;
 	char *gitdir;
 	char *gitcommondir;
 	char *packed_refs_path;

@@ -982,22 +976,14 @@ static void clear_loose_ref_cache(struct files_ref_store *refs)
  * Create a new submodule ref cache and add it to the internal
  * set of caches.
  */
-static struct ref_store *files_ref_store_create(const char *submodule)
+static struct ref_store *files_ref_store_create(const char *gitdir)
 {
 	struct files_ref_store *refs = xcalloc(1, sizeof(*refs));
 	struct ref_store *ref_store = (struct ref_store *)refs;
 	struct strbuf sb = STRBUF_INIT;
-	const char *gitdir = get_git_dir();
 
 	base_ref_store_init(ref_store, &refs_be_files);
 
-	if (submodule) {
-		refs->submodule = xstrdup(submodule);
-		refs->packed_refs_path = git_pathdup_submodule(
-			refs->submodule, "packed-refs");
-		return ref_store;
-	}
-
 	refs->gitdir = xstrdup(gitdir);
 	get_common_dir_noenv(&sb, gitdir);
 	refs->gitcommondir = strbuf_detach(&sb, NULL);

@@ -1014,8 +1000,7 @@ static struct ref_store *files_ref_store_create(const char *submodule)
 static void files_assert_main_repository(struct files_ref_store *refs,
 					 const char *caller)
 {
-	if (refs->submodule)
-		die("BUG: %s called for a submodule", caller);
+	/* This function is to be deleted in the next patch */