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/cat-file.c

@@ -191,7 +191,7 @@ static int cat_one_file(int opt, const char *exp_type, const char *obj_name,
 			const char *ls_args[3] = { NULL };
 			ls_args[0] =  "ls-tree";
 			ls_args[1] =  obj_name;
-			ret = cmd_ls_tree(2, ls_args, NULL);
+			ret = cmd_ls_tree(2, ls_args, NULL, the_repository);
 			goto cleanup;
 		}
 
@@ -923,7 +923,10 @@ static int batch_option_callback(const struct option *opt,
 	return 0;
 }
 
-int cmd_cat_file(int argc, const char **argv, const char *prefix)
+int cmd_cat_file(int argc,
+		 const char **argv,
+		 const char *prefix,
+		 struct repository *repo UNUSED)
 {
 	int opt = 0;
 	int opt_cw = 0;