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/for-each-repo.c

@@ -29,7 +29,10 @@ static int run_command_on_repo(const char *path, int argc, const char ** argv)
 	return run_command(&child);
 }
 
-int cmd_for_each_repo(int argc, const char **argv, const char *prefix)
+int cmd_for_each_repo(int argc,
+		      const char **argv,
+		      const char *prefix,
+		      struct repository *repo UNUSED)
 {
 	static const char *config_key = NULL;
 	int keep_going = 0;