[m-rev.] diff: Fix value of maybe_string option when negated.

[Julien Fischer]

Hi Peter,

On Tue, 8 Nov 2022, Peter Wang wrote:

> library/getopt.m:
> library/getopt_io.m:
>    Fix bug where a negation option (--no-foo) would set the value of a
>    maybe_string option to maybe_int(no) instead of maybe_string(no)
>    in the option table.

It looks like this will need to go on to the release branch as well.
It would be good to have a regression test for this one as well.

Julien.