push: teach --quiet to suppress "Everything up-to-date"

This should have been part of 481c7a6, whose goal was to
make "git push -q" silent unless there is an error.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

transport.c

@@ -1042,7 +1042,7 @@ int transport_push(struct transport *transport,
 				update_tracking_ref(transport->remote, ref, verbose);
 		}
 
-		if (!ret && !refs_pushed(remote_refs))
+		if (!quiet && !ret && !refs_pushed(remote_refs))
 			fprintf(stderr, "Everything up-to-date\n");
 		return ret;
 	}