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>

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;
 }
 

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)
+	/* This function is to be fixed up in the next patch */
-		die("BUG: %s called for a submodule", caller);
 }
 
 /*
@@ -1206,11 +1191,6 @@ static void files_ref_path(struct files_ref_store *refs,
 			   struct strbuf *sb,
 			   const char *refname)
 {
-	if (refs->submodule) {
-		strbuf_git_path_submodule(sb, refs->submodule, "%s", refname);
-		return;
-	}
-
 	switch (ref_type(refname)) {
 	case REF_TYPE_PER_WORKTREE:
 	case REF_TYPE_PSEUDOREF:

refs/refs-internal.h

@@ -482,12 +482,11 @@ struct ref_store;
 /* refs backends */
 
 /*
- * Initialize the ref_store for the specified submodule, or for the
+ * Initialize the ref_store for the specified gitdir. These functions
- * main repository if submodule == NULL. These functions should call
+ * should call base_ref_store_init() to initialize the shared part of
- * base_ref_store_init() to initialize the shared part of the
+ * the ref_store and to record the ref_store for later lookup.
- * ref_store and to record the ref_store for later lookup.
  */
-typedef struct ref_store *ref_store_init_fn(const char *submodule);
+typedef struct ref_store *ref_store_init_fn(const char *gitdir);
 
 typedef int ref_init_db_fn(struct ref_store *refs, struct strbuf *err);