http-push: disable http-push without USE_CURL_MULTI

Make http-push always fail when not compiled with USE_CURL_MULTI, since
otherwise it corrupts the remote repository (and then fails anyway).
Signed-off-by: NGrégoire Barbier <gb@gbarbier.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

http-push.c

@@ -2212,6 +2212,10 @@ int main(int argc, char **argv)
 		break;
 	}
 
+#ifndef USE_CURL_MULTI
+	die("git-push is not available for http/https repository when not compiled with USE_CURL_MULTI");
+#endif
+
 	if (!remote->url)
 		usage(http_push_usage);