bug#66187: read-file-name unexpected behavior when MUSTMATCH is a function

[Stefan Monnier]

>> then how about not breaking the
>> behavior of REQUIRE-MATCH at all, and instead
>> just add a separate argument for what a function
>> value of REQUIRE-MATCH does in 29.1?
>
> That is definitely not a change suitable for Emacs 29 at this point.

Not only that but that would be hideous over-engineering (so not
suitable for `master` either).
The use of a function for `require-match` is already extremely rare
(we've had `require-match` for more than 30 years and it's only last
year that we decided it was worth generalizing it to a function), and
the new proposed behavior is strictly more general than the
29.1 behavior.


        Stefan