Re: RCS, again: another removed functionality: undo last-checkin

[Dmitry Gutov <dgutov@yandex.ru>]

On 10/01/2015 08:52 PM, Eli Zaretskii wrote:

> I indeed think that features should rarely be removed, only added.

Then you must be prepared that at certain point the cost of improving 
Emacs will be too much for anyone to do anything of significance to it.

> Yes, but different VCSes have different internal logic, so something
> might make sense with RCS, but not with Git, or vice versa.  That's
> the crux of the problem we are discussing, I think, so the question is
> whether a feature must make sense for every back-end for it to be
> considered as sensible.

It may be decided on a case-by-case basis, but the question is rather 
whether it *could* be decided at all. The exact criterion, "make sense 
for at least a half of all backends", or "make sense in at least one of 
the modern backends", is up for discussion.

> I disagree that this sacrifice is always possible, let
> alone desirable.  Especially when the change in the workflow boils
> down to "do it from outside Emacs".

I still think it's just fine for rare operations. Even those performed 
regularly, but at long-ish intervals.

> I think there's a better alternative: start a new front end, which
> will only support a subset of back-ends.  Then the elders can
> peacefully continue using the old front-end, which will more or less
> stop being developed, only maintained whenever some of the
> infrastructure changes absolutely require that.

It's an option indeed, though one that requires a larger investment of 
time (which we don't have a lot of to spare). And what if we make some 
unfortunate decision WRT to features when creating the second front-end, 
too? Wait a few years and create a third one?

It also assumes that the set of backend commands can be static without 
incurring any cost. Whereas the most recent overhaul by ESR featured 
some beneficial changes in it.

> Muscle memory is what stopping them.  It's a powerful thing.

It's easier to change than a big codebase full of features one is 
absolutely not allowed to break.