Stephen Berman <stephen.berman@gmx.net> writes:
> For the other regression, here is a reproducer:
>
> 0. mkdir /tmp/{Test,retest}
> 1. emacs -Q --eval "(custom-set-variables                        \
>    '(completion-category-overrides '((file (styles substring)))) \
>    '(read-file-name-completion-ignore-case t))"
> 2. Type `C-x d /tmp/tes TAB': this completes to /tmp/test/
> 3. Type TAB again: Emacs dings and shows "[no match]"
>
> If you repeat this recipe in emacs-30, then after the TAB in step 3, this
> completion is shown: /tmp/Test/. and typing TAB again pops up the
> *Completions* buffer displaying the two completions ../ and ./
>
> While the result in emacs-30 seems suboptimal, since it omits the
> possible completion /tmp/retest/, still it's better than "[no match]".
>
> A workaround for both emacs-30 and master is to enter at step 2 `C-x d
> /tmp/*tes TAB'. This shows the completion /tmp/*test/, then hitting TAB
> again shows /tmp/*test/., and hitting TAB a third time pops up the
> *Completions* buffer showing the four completions Test/../, Test/./,
> retest/../, and retest/./
>
> Steve Berman

Thanks for the prompt and detailed report.  Does the attached patch fix
this issue for you?