bug#66542: Fix: locate-dominating-file predicate should receive dir not file

[Eli Zaretskii <eliz@gnu.org>]

> From: dalanicolai <dalanicolai@gmail.com>
> Date: Sat, 21 Oct 2023 17:39:17 +0200
> Cc: 66542@debbugs.gnu.org
> 
> You are right (of course :)
> So I have attached another patch which only strips the file name (applies file-name-directory) if the file
> is not a directory.
> 
> If the file is not a directory, then that stripped name should also be returned by the function, i.e. in the
> 'cond`, root should be set to the stripped file name. Therefore, the patched version simply 'checks
> and sets' the file name first inside the setq.
> 
> Also, now we can remove the check in the first clause of the 'if' (of 'setq try'), because 'file' is
> guaranteed to be a directory name, and the existence of the directory name is already checked by
> the 'file-exists-p'.
> 
> This change does not affect other parts of the function (except that it speeds it up a little, because it
> excludes the cycles, that only strip the file names in case file is a 'real' file.
> Indeed, the function should only check for 'parent directories' (not files).

Thanks, installed on master, and closing the bug.