bug#50572: 28.0.50; [PATCH] fix VC to find the responsible backend with the most specific path.

[Juri Linkov]

>> I thought that we might already have a function for this. Does counting
>> slashes will work with Windows path?
>
> Hm...  Actually, I'm not sure.  Perhaps doing a series of
> file-name-directory/directory-file-name in a loop (to peel off the
> directory components) would be the best algorithm here?  And I don't
> think we have a function for this -- at least I can't find anything
> promising while poking around.

ffap-list-env contains such comment:

  ;; Similar: dired-split, TeX-split-string, and RHOGEE's psg-list-env
  ;; in ff-paths and bib-cite.  The EMPTY arg may help mimic kpathsea.

And indeed dired-split is used in dired-aux.el like this:

  (dired-split "/" dir1)

I don't know if this works on Windows.