packfile: only prepare owning store in packfile_store_prepare()

When calling `packfile_store_prepare()` we prepare not only the provided
packfile store, but also all those of all other sources part of the same
object database. This was required when the store was still sitting on
the object database level. But now that it sits on the source level it's
not anymore.

Refactor the code so that we only prepare the single packfile store
passed by the caller. Adapt callers accordingly.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

builtin/grep.c

@@ -1213,12 +1213,14 @@ int cmd_grep(int argc,
 		 */
 		if (recurse_submodules)
 			repo_read_gitmodules(the_repository, 1);
-		/*
-		 * Note: `packfile_store_prepare()` prepares stores from all
-		 * sources. This will be fixed in a subsequent commit.
-		 */
-		if (startup_info->have_repository)
-			packfile_store_prepare(the_repository->objects->sources->packfiles);
+
+		if (startup_info->have_repository) {
+			struct odb_source *source;
+
+			odb_prepare_alternates(the_repository->objects);
+			for (source = the_repository->objects->sources; source; source = source->next)
+				packfile_store_prepare(source->packfiles);
+		}
 
 		start_threads(&opt);
 	} else {

packfile.c

@@ -1063,16 +1063,11 @@ static int sort_pack(const struct packfile_list_entry *a,
 
 void packfile_store_prepare(struct packfile_store *store)
 {
-	struct odb_source *source;
-
 	if (store->initialized)
 		return;
 
-	odb_prepare_alternates(store->source->odb);
-	for (source = store->source->odb->sources; source; source = source->next) {
-		prepare_multi_pack_index_one(source);
-		prepare_packed_git_one(source);
-	}
+	prepare_multi_pack_index_one(store->source);
+	prepare_packed_git_one(store->source);
 
 	sort_packs(&store->packs.head, sort_pack);
 	for (struct packfile_list_entry *e = store->packs.head; e; e = e->next)
@@ -2098,15 +2093,11 @@ static int find_pack_entry(struct repository *r,
 {
 	struct odb_source *source;
 
-	/*
-	 * Note: `packfile_store_prepare()` prepares stores from all sources.
-	 * This will be fixed in a subsequent commit.
-	 */
-	packfile_store_prepare(r->objects->sources->packfiles);
-
-	for (source = r->objects->sources; source; source = source->next)
+	for (source = r->objects->sources; source; source = source->next) {
+		packfile_store_prepare(r->objects->sources->packfiles);
 		if (source->midx && fill_midx_entry(source->midx, oid, e))
 			return 1;
+	}
 
 	for (source = r->objects->sources; source; source = source->next) {
 		struct packfile_list_entry *l;