bug#26911: 25.2; eshell "cd .." doesn't work correctly with TRAMP

[Eli Zaretskii]

> Cc: 26911@debbugs.gnu.org, mattiase@acm.org, michael.albinus@gmx.de,
>  yegortimoshenko@gmail.com
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Sat, 29 Aug 2020 09:46:29 -0700
> 
> >> I installed the attached patch to revert the recent expand-file-changes in 
> >> the
> >> DOS_NT case, which should fix the problem you mentioned.
> > 
> > Thanks, it does.  But it produces a different problem:
> > 
> >    (expand-file-name "." "c:/foo/bar/") => "c:/foo/bar
> > 
> > (note the absence of the trailing slash).
> 
> That's what Emacs 27 does on MS-Windows, no? So it's not a regression, and 
> the 
> problem can be fixed at the convenience of whoever's interested in hacking on 
> the MS-Windows side of the code.

It's a regression wrt behavior on Posix platforms: it fails one of the
tests in fileio-tests.el:

  Test fileio-tests--HOME-trailing-slash condition:
      (ert-test-failed
       ((should
         (equal
          (expand-file-name "~")
          (expand-file-name home)))
        :form
        (equal "c:/a/b/c" "c:/a/b/c/")
        :value nil :explanation
        (arrays-of-different-length 8 9 "c:/a/b/c" "c:/a/b/c/" 
first-mismatch-at 8)))
     FAILED   1/12  fileio-tests--HOME-trailing-slash (0.000000 sec)

> Another way to put it is that Bug#26911 is now fixed for GNU and POSIX, but 
> not 
> for MS-Windows. My earlier changes attempted to fix it for all platforms, but 
> this had undesirable side-effects in MS-Windows so I withdrew the MS-Windows 
> part of the changes. I have therefore reopened Bug#26911 since I assume it's 
> still present on MS-Windows.

If that is the case, I prefer that we revert all the changes made
recently to fix bug#26911, and leave that bug open, until a fix is
available that works on all platforms.

> > I'm not interested in messing with expand-file-name
> 
> That's understandable as expand-file-name is quite a mess internally. But if 
> you're not interested in any attempt to clean up the mess, I guess I should 
> refrain from giving it a shot.

Fine with me, then let's revert the recent changes and go back to what
we had before.

Thanks for trying to fix that.