builtin: add a repository parameter for builtin functions

In order to reduce the usage of the global the_repository, add a
parameter to builtin functions that will get passed a repository
variable.

This commit uses UNUSED on most of the builtin functions, as subsequent
commits will modify the actual builtins to pass the repository parameter
down.

Signed-off-by: John Cai <johncai86@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/repack.c

@@ -1116,7 +1116,10 @@ static const char *find_pack_prefix(const char *packdir, const char *packtmp)
 	return pack_prefix;
 }
 
-int cmd_repack(int argc, const char **argv, const char *prefix)
+int cmd_repack(int argc,
+	       const char **argv,
+	       const char *prefix,
+	       struct repository *repo UNUSED)
 {
 	struct child_process cmd = CHILD_PROCESS_INIT;
 	struct string_list_item *item;