bug#68022: 30.0.50; File cache completions accumulate instead of replacing minibuffer input

[Eshel Yaron via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Mon, 25 Dec 2023 07:54:22 +0100
>> From:  Eshel Yaron
>>
>> With emacs -Q:
>>
>> 1. M-x file-cache-add-directory-using-find /path/to/emacs/
>> 2. C-x C-f mini C-TAB
>> 3. Observe the *Completions* buffer pop up with file cache
>> completions, suggesting as usual to "type M-<down> or M-<up> to move
>> point between completions."
>> 4. M-<down> M-<down> M-<up> ...
>> 5. Each candidate you highlight this way is inserted in the minibuffer
>> after the current input, instead of replacing the appropriate part of
>> the input.
>>
>> I see this already in Emacs 29.1, FWIW.
>
> Something is missing in the recipe above, because I get "No match"
> when I press C-TAB in step 2.  What did I miss?

Hmm, I'm not sure.  Perhaps `file-cache-add-directory-using-find` didn't
do its job for some reason?  The point is just to add a bunch of file
names to the cache.

> Is the above supposed to work in any Emacs source tree?  Also, what
> should be the default-directory in step 1 (if it's important) --
> should it be the root of the Emacs source tree?

That shouldn't matter, I think, as long as you have several files with
"mini" in their names in the cache.  Any other invocation of `C-TAB`
that pops the *Completions* buffer should show the same behavior AFAICT.