When multiple commands with common prefix are registered, calling `--help` with the prefix should list them all

[jakub-g]

Context

Consider this code:

const { Command } = require('clipanion');

class TypecheckCommand extends Command {
    static paths = [['typecheck']];
    ...
}

class TypecheckStopCommand extends Command {
    static paths = [['typecheck', 'stop']];
    ...
}

module.exports = [TypecheckCommand, TypecheckStopCommand];

Current behavior

yarn cli typecheck --help prints only info about typecheck itself.

Expected behavior

It should at least indicate the existence of the other subcommands (in this case yarn cli typecheck stop).

[Drarig29]

In the same vein, I think that with this code:

const { Command } = require('clipanion');

class TypecheckStartCommand extends Command {
    static paths = [['typecheck', 'start']]; // I know it doesn't make sense, but that's for the example
    ...
}

class TypecheckStopCommand extends Command {
    static paths = [['typecheck', 'stop']];
    ...
}

module.exports = [TypecheckStartCommand, TypecheckStopCommand];

The output should not show:

Unknown Syntax Error: Command not found; did you mean one of:

0. yarn cli typecheck start
1. yarn cli typecheck stop

While running cli typecheck --help

But rather exactly the same output as the built-in --help, but just filtered out.

[Drarig29]

What do you think @arcanis?

I can work on a PR if you accept the suggestion.