clone: detect extra arguments

If git clone is given more than two non-option arguments, it
silently throws away all but the first one.  Complain instead.

Discovered by comparing the new builtin clone to the old
git-clone.sh.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-clone.c

@@ -379,8 +379,13 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, builtin_clone_options,
 			     builtin_clone_usage, 0);
 
+	if (argc > 2)
+		usage_msg_opt("Too many arguments.",
+			builtin_clone_usage, builtin_clone_options);
+
 	if (argc == 0)
-		die("You must specify a repository to clone.");
+		usage_msg_opt("You must specify a repository to clone.",
+			builtin_clone_usage, builtin_clone_options);
 
 	if (option_mirror)
 		option_bare = 1;