On Thu, Nov 10, 2022 at 07:06:00PM +0000, Victoria Dye via GitGitGadget wrote:

Changes since V2
================

 * Cleaned up option handling & provided more informative error messages in
   'test-tool cache-tree'. The changes don't affect any behavior in the
   added tests & 'test-tool cache-tree' won't be used outside of
   development, but the improvements here will help future readers avoid
   propagating error-prone implementations.
   * Note that the suggestion to change the "unknown subcommand" error to a
     'usage()' error was not taken, as it would be somewhat cumbersome to
     use a formatted string with it.

I'm not sure I understand what's cumbersome.  It's as simple as:

   if (...) {
       error(_("unknown subcommand: `%s'"), argv[0]);
       usage_with_options(test_cache_tree_usage, options);
   }

     This is in line with other custom
     subcommand parsing in Git, such as in 'fsmonitor--daemon.c'.

The option parsing in 'fsmonitor--daemon.c' is broken, please don't
consider it as an example to follow.