submodule: check argc count for git submodule--helper clone

Extra unused arguments to git submodule--helper clone subcommand were
being silently ignored. Add a check to the argc count after options
handling to ensure that no extra arguments were left on the argv array.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/submodule--helper.c

@@ -194,6 +194,10 @@ static int module_clone(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, module_clone_options,
 			     git_submodule_helper_usage, 0);
 
+	if (argc)
+		usage_with_options(git_submodule_helper_usage,
+				   module_clone_options);
+
 	strbuf_addf(&sb, "%s/modules/%s", get_git_dir(), name);
 	sm_gitdir = strbuf_detach(&sb, NULL);