Re: New git-rebase backend: no way to drop already-empty commits

[Bryan Turner <bturner@atlassian.com>]

On Tue, Apr 7, 2020 at 10:58 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> Elijah Newren <newren@gmail.com> writes:
>
> > Yes, from the manpage:
> >
> > ...
> >
> > and
> >
> > """
> > Empty commits
> > ~~~~~~~~~~~~~
> >
> > The apply backend unfortunately drops intentionally empty commits, i.e.
> > commits that started empty, though these are rare in practice.  It
> > also drops commits that become empty and has no option for controlling
> > this behavior.
>
> This is a very good illustration that shows why "switch the default
> and retire the apply backend" deserves to be cooked for quite a long
> time.  The 'apply' dropping empty commits may have looked like an
> 'unfortunate' thing to whoever wrote the above paragraph in the
> documentation, but it clearly shows that person (me included) did
> not think of the ramifications deeply enough that there may be valid
> workflows that _depend_ on the behaviour.
>
> As we will be dropping 'apply' that could be used as an escape
> hatch, before we do so, we should teach the other backends an
> alternate escape hatch to help those who have been depending on the
> behaviour of 'apply' that discards the empty ones, whether they
> become empty, or they are empty from the beginning.  I think the
> "has contents originally but becomes empty" side is already taken
> care of, so we'd need to make sure it is easy to optionally discard
> the ones that are originally empty.

I wonder if the existing --empty could be extended, such that "drop"
was treated as a (deprecated?) synonym for "drop-new" (a new entry in
the list), with a new "drop-all". That way end users could pass
--empty=drop-all to get the old "apply" behavior with "merge".
Something like "--empty={drop-all,drop-new[,drop],keep,ask}::". A name
like "drop-all" seems more obvious/intuitive than simply "all" or
"always".

Just a thought from someone else who was also bitten by this behavior change.

>
> Thanks.