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/verify-commit.c

@@ -51,7 +51,10 @@ static int verify_commit(const char *name, unsigned flags)
 	return run_gpg_verify((struct commit *)obj, flags);
 }
 
-int cmd_verify_commit(int argc, const char **argv, const char *prefix)
+int cmd_verify_commit(int argc,
+		      const char **argv,
+		      const char *prefix,
+		      struct repository *repo UNUSED)
 {
 	int i = 1, verbose = 0, had_error = 0;
 	unsigned flags = 0;