bug#62693: 28.2; VC: CVS: Fix lost file reporting and enable reverting it

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 15 Apr 2023 01:59:28 +0300
> Cc: 62693@debbugs.gnu.org
> From: Dmitry Gutov <dmitry@gutov.dev>
> 
> On 13/04/2023 19:40, Olivier Certner wrote:
> > Hi,
> > 
> > Thanks for looking at this.
> > 
> >> - Could you explain what kind of files are not listed and when? I'm
> >> guessing this has to do with the file name? I've tried to reproduce the
> >> problem with a file name that contained a space, and couldn't see it.
> > 
> > It's not that files are not listed, they are so always. As said, the problem
> > is their name. For example, if I remove an INSTALL file in a repository,
> > `INSTALL' is the name listed in a VC dir buffer, *quotes included*. Then, no
> > VC operation can work because there is indeed no file by this name (with
> > quotes, both in the filesystem or known by CVS).
> 
> So the actual file name is not the problem -- the problem happens with 
> removed files?
> 
> Okay, I can see that now: when the file is removed, it's displayed 
> (incorrectly) with quotes around its name. Patches 2 and 3 do fix the 
> remove - vc-dir - vc-revert scenario.
> 
> Eli, do we want these fixes in emacs-29? These are again not 
> regressions, but I'm guessing users of CVS are foremost to benefit from 
> adding this to the upcoming release.

The patch is AFAICS basically a complete rewrite of an important
function, so I don't see how I could agree applying this to the
release branch.  Sorry.  (Was the introduction of so many CL-isms
really necessary, btw?)

As a minor nit, please don't use "path" or "PATH" for anything except
$PATH-style lists of directories, as GNU Coding Standards frown on
such use of this word.  We use "file name" or "directory name" or
"leading directories" (as the case may be) instead.

> Regarding the new patch, it's great to see the list of examples, but 
> could you instead move it to a test or several inside 
> test/lisp/vc/vc-cvs-tests.el? This file does not exist yet, but you can 
> use vc-git-test.el as an example, in the same directory.

Yes, having a test for this would be most welcome.