(The "legacy" comment was that it was fairly simple and different to what is displayed in the subcommand help, but had displayed that way for a long time and I didn't have a reason to change it when I rewrote the help.)

Some thoughts, no conclusions yet!

High level, this is doing same as displaying cmd.usage() if there is a custom usage. So why don't we just call cmd.usage() all the time?

A high level concern is that in the display of the help for the command, the usage and the description are displayed on separate lines.

% node plain.js busy --help
Usage: plain busy|bz [options] <file>

bells and whistle
...

When listing the subcommands, we add the description directly after the usage:

% node plain.js --help 
...
Commands:
  simple                      no arguments no options
  busy|bz [options] <file>    bells and whistle
...

(Side note: by default every command gets [options]in its full help "usage" because of the help option. Which does cause complaints anyway, so maybe we could change that small part!)

The usage generated by Commander is pretty simplistic. Unix commands often show at least all the single letter options, and sometimes multiple lines of different use cases in the synopsis. That isn't the thing we are trying to solve here, but it does suggest that custom usage lines may be longer than the simple default one.

For example man ls includes:

SYNOPSIS
     ls [-@ABCFGHILOPRSTUWabcdefghiklmnopqrstuvwxy1%,] [--color=when] [-D format] [file ...]

We had a similar problem with the description, that a long description is good for the full help but may suck when displaying in a list of subcommands. To solve that we added .summary() to optionally supply a different (likely shorter) version of the description.

Currently, this can be fixed by reconfiguring the helper, which is fine, but it would be nice to have this functionality by default.

If is fairly easy to display full usage, but I acknowledge that if it is extra work.

function fullUsage(cmd) {
  const cmdNames = cmd.name() + (cmd.alias() ? '|' + cmd.alias() : '');
  return cmdNames + ' ' + cmd.usage();
  }

program.configureHelp({ subcommandTerm: fullUsage });

(Good detail in the Pull Request description, thanks.)

I am guessing this is something you wanted in one of your programs. Have you got some examples of what you put in custom command usage?

(I am leaving this open for a month to see if gets any feedback from other people.)

I am interested in improving the usage displayed for subcommands. I don't think using the custom usage is the answer though. In the general case I think the usage in the list of subcommands benefits from being terse.

The approach we took with the subcommand description was adding an optional summary, so there could be a usageSummary. That does not help with the original issue in this PR, and is a separate idea.

Since the goal of using custom usage can be achieved with a reasonably simple override (#1853 (comment)), closing this PR.

Thank you for your contributions.