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

[David Kastrup <dak@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Dmitry Gutov <dgutov@yandex.ru>
>> Date: Mon, 21 Sep 2015 02:24:22 +0300
>> 
>> On 09/20/2015 07:30 PM, Stefan Monnier wrote:
>> 
>> > The most natural way to re-add tihs feature is to make vc-rcs.el
>> > understand the "Amend:" header that's also used by Git.
>> 
>> The use case may be similar, but the name "rollback" sounds much closer 
>> to what happen when you call 'git reset [--hard]'. Which is a useful 
>> operation as well, one currently not supported by VC.
>
> If the commit was already pushed, you will need "git revert" instead,
> I think.

That depends on whether you are working on a branch considered to have
dependable commits or a preparatory/review branch.  People are expected
to deal with warped histories on preparatory branches.  As an example,
LilyPond works with a "staging" branch and a "master" branch.  "master"
only moves forward: once a commit is in there, it stays.  If its effects
are to be annulled, it is reverted.  Nobody pushes to master though.
Any changes are instead pushed to staging.  An automated task picks up
staging every few hours and if it has progressed ahead of master, it
makes a complete build of the state of staging, a documentation build, a
run of all regtests, and when all of that succeeds, it pushes the tested
state on top of master (only as a fast-forward, otherwise it fails.  And
it also tests that the current state of staging is the same or strictly
ahead of the tested state, so you can "stop the clock" any time before
the automated tests finish).  Every few months, someone will push
something to staging that does not pass the whole tests and builds.  In
that case the machinery stops before pushing anything to master, and
staging needs to be cleaned up.  This is not done with reverts but by
resetting the branch appropriately in spite of it being a public branch.

That's because people are expected not to maintain their personal
versions of the "staging" branch from which dropped changes could be
reintroduced.

-- 
David Kastrup