Re: RCS: (vc-next-action 1) only New Backend

[Eli Zaretskii <eliz@gnu.org>]

> From: David Kastrup <dak@gnu.org>
> Cc: oub@mat.ucm.es,  emacs-devel@gnu.org
> Date: Sat, 19 Sep 2015 12:00:45 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: David Kastrup <dak@gnu.org>
> >> Cc: Eli Zaretskii <eliz@gnu.org>,  emacs-devel@gnu.org
> >> Date: Sat, 19 Sep 2015 10:59:24 +0200
> >> 
> >> I seem to remember that some RCS-only features were debated and possibly
> >> dropped at that time because ESR (along with a lot of others) were not
> >> terribly sympathetic towards complicating the generic framework because
> >> of the possibility of its continued use (mostly expected to be due to
> >> nostalgia).
> >
> > I guess you are referring to this discussion:
> >
> >   http://lists.gnu.org/archive/html/emacs-devel/2014-12/msg01164.html
> >
> > It talks about "rollback", whereas it seems that what was removed
> > includes a possibility to tell RCS how to number the version it is
> > about to commit.
> 
> Entirely possible that this is what I remembered.  However, the
> responsible commit turns out to be a good match to my vague recollection
> regarding content, commit message, date and author:
> 
> commit 2f4f92007956983e6f5cb5136a57ddaa0cd9428e
> Author: Eric S. Raymond <esr@thyrsus.com>
> Date:   Mon Dec 1 06:23:10 2014 -0500
> 
>     VC API simplification: remove ability to set initial revision.
>     
>     This hasn't made any sense since RCS, and was a dumb stunt then.
>     
>     * vc/vc.el and all backends: API simplification; init-revision is
>     gone, and vc-registered functions no longer take an initial-revision
>     argument.
> 
> and so my comments regarding the likely reaction to a wish for
> resurrection of that feature are probably not wide off the mark.

I already resurrected it.

The motivation for removing that functionality was that it complicates
the back-ends.  I've made the REVISION argument to back-end's checkin
method optional and silently ignored by back-ends that don't support
it, so I don't think the back-ends should be affected, except by
having that optional ignored arg.

There was a similar ability in vc-register.  I didn't restore it,
because one can now register as usual and then immediately checkin a
change with a specific version, thus allowing a reasonably convenient
workaround without any need to change the back-ends yet again.

(If I knew that removing this "rollback" also removes the ability to
force a revision at checkin time, I'd have objected to the removal.
But that never came up, AFAIR; instead, the only issue discussed at
length was the meaning of "rollback" for modern VCSes.)