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/tag.c

@@ -457,7 +457,10 @@ static int strbuf_check_tag_ref(struct strbuf *sb, const char *name)
 	return check_refname_format(sb->buf, 0);
 }
 
-int cmd_tag(int argc, const char **argv, const char *prefix)
+int cmd_tag(int argc,
+	    const char **argv,
+	    const char *prefix,
+	    struct repository *repo UNUSED)
 {
 	struct strbuf buf = STRBUF_INIT;
 	struct strbuf ref = STRBUF_INIT;