refs: store the main ref store inside the repository struct

This moves the 'main_ref_store', which was a global variable in refs.c
into the repository struct.

This patch does not deal with the parts in the refs subsystem which deal
with the submodules there. A later patch needs to get rid of the submodule
exposure in the refs API, such as 'get_submodule_ref_store(path)'.

Acked-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -1608,9 +1608,6 @@ static struct ref_store_hash_entry *alloc_ref_store_hash_entry(
 	return entry;
 }
 
-/* A pointer to the ref_store for the main repository: */
-static struct ref_store *main_ref_store;
-
 /* A hashmap of ref_stores, stored by submodule name: */
 static struct hashmap submodule_ref_stores;
 
@@ -1652,13 +1649,13 @@ static struct ref_store *ref_store_init(const char *gitdir,
 	return refs;
 }
 
-struct ref_store *get_main_ref_store_the_repository(void)
+struct ref_store *get_main_ref_store(struct repository *r)
 {
-	if (main_ref_store)
-		return main_ref_store;
+	if (r->refs)
+		return r->refs;
 
-	main_ref_store = ref_store_init(get_git_dir(), REF_STORE_ALL_CAPS);
-	return main_ref_store;
+	r->refs = ref_store_init(r->gitdir, REF_STORE_ALL_CAPS);
+	return r->refs;
 }
 
 /*

refs.h

@@ -760,9 +760,7 @@ int reflog_expire(const char *refname, const struct object_id *oid,
 
 int ref_storage_backend_exists(const char *name);
 
-#define get_main_ref_store(r) \
-	get_main_ref_store_##r()
-struct ref_store *get_main_ref_store_the_repository(void);
+struct ref_store *get_main_ref_store(struct repository *r);
 /*
  * Return the ref_store instance for the specified submodule. For the
  * main repository, use submodule==NULL; such a call cannot fail. For

refs/files-backend.c

@@ -61,10 +61,6 @@ struct ref_lock {
 	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;

repository.h

@@ -26,6 +26,9 @@ struct repository {
 	 */
 	struct raw_object_store *objects;
 
+	/* The store in which the refs are held. */
+	struct ref_store *refs;
+
 	/*
 	 * Path to the repository's graft file.
 	 * Cannot be NULL after initialization.