Joseph Turner <joseph@breatheoutbreathe.in> writes:

> Philip Kaludercic <philipk@posteo.net> writes:
>
>> Joseph Turner <joseph@breatheoutbreathe.in> writes:
>>
>>>                                                  However, the behavior of
>>> read-file-name is unspecified when a MUSTMATCH function returns nil:
>>>
>>> - a function, which will be called with the input as the
>>>   argument.  If the function returns a non-nil value, the
>>>   minibuffer is exited with that argument as the value.
>>>
>>> Is this a bug, a case of under-documentation, or do I misunderstand something?
>>>
>>> I'm happy to post this in a separate bug thread if you think it's worth it.
>>
>> Perhaps that would be worth doing, that way the people who know more
>> about completion than I do would be more likely to see it and help
>> out.
>
> Okay, thanks! I'll do that.

Now that #66187
(<https://yhetil.org/emacs-bugs/87cytlqmqh.fsf@breatheoutbreathe.in/>)
and bug#68815
(<https://yhetil.org/emacs-bugs/8734ufyxoy.fsf@breatheoutbreathe.in/>)
are fixed on emacs-29, I'm revisiting this issue.

With the following patch, the interactive prompt in package-vc-checkout
now offers all directory for completion (empty or not), but only exits
when the minibuffer contains an empty directory or nonexistent filename.

Testing this patch requires checking out emacs-29 after e6c82fe35e3.

Thanks!

Joseph