quoted

+ argc = parse_options(argc, argv, prefix, options, repo_usage, 0);
+
+ if (fn) {
+ return fn(argc, argv, prefix, repo);
+ } else {
+ if (argc) {
+ error(_("unknown subcommand: `%s'"), argv[0]);
+ usage_with_options(repo_usage, options);
+ }
+ return 1;

I think we need to print an error `if (!argc)`, as well. Otherwise the
user wouldn't know why `git repo` without any argumentsdoesn't do
anything.

Actually, it already does it! The subcommand parsing introduced in fa83cc834d
(parse-options: add support for parsing subcommands, 2022-08-19) displays
"error: need a subcommand" and the command usage when no subcommand is provided.

Actually, this whole if-else can be removed. When an invalid command is
provided, the execution is aborted in parse_options, so it's safe to assume that
fn is a valid function.

I'll change that.