Allow readonly arrays to be used as choices

[Pzixel]

Consider following usage:

const SupportedDrinks = ['small', 'medium', 'large'] as const;
type Drink = typeof SupportedDrinks[number];

const program = new Command()
      .addOption(new Option('-d, --drink <size>', 'drink size').choices(SupportedDrinks))

This allows user to get a strongly typed enum and reuse it to automatically populate supported drinks.
This code doesn't compile now though since readonly array is not assignable to just string[].

Pull Request

Problem

Solution

ChangeLog

[Pzixel]

Sorry I didn't see there is a template for PRs, I've just sent it via regular "edit-and-create-PR" flow. Should I add any tests/more motivation here?

[shadowspawn]

This will be supported in Commander 9. See #1667. That PR started out fairly small too, but we then made code changes to make the usage of the parameters more robustly readonly.

Two PRs in quick succession, so readonly is something people are hitting. 😄

[Edit: corrected PR link. Twice!]

[Pzixel]

1679 is this PR, you probably meant to mention something else... 😅

[shadowspawn]

Cough. Try this one: #1667