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Re: Git Evolve

If you're curious how the Mercurial absorb command works, here's the code:


It's GPL 2:


On Tue, Oct 2, 2018 at 2:11 AM, Ævar Arnfjörð Bjarmason
<avarab@xxxxxxxxx> wrote:
> On Tue, Oct 02 2018, Taylor Blau wrote:
>> Hi Stefan,
>> On Sat, Sep 29, 2018 at 04:00:04PM -0700, Stefan Xenos wrote:
>>> Hello, List!
>>> I'm interested in porting something like Mercurial's evolve command to
>>> Git.
>> Welcome to Git :-). I think that the discussion in this thread is good,
>> but it's not why I'm replying. I have also wanted a Mercurial feature in
>> Git, but a different one than yours.
>> Specifically, I've wanted the 'hg absorb' command. My understanding of
>> the commands functionality is that it builds a sort of flamegraph-esque
>> view of the blame, and then cascades downwards parts of a change. I am
>> sure that I'm not doing the command justice, so I'll defer to [1] where
>> it is explained in more detail.
>> The benefit of this command is that it gives you a way to--without
>> ambiguity--absorb changes into earlier commits, and in fact, the
>> earliest commit that they make sense to belong to.
>> This would simplify my workflow greatly when re-rolling patches, as I
>> often want to rewrite a part of an earlier commit. This is certainly
>> possible by a number of different `git rebase` invocations (e.g., (1)
>> create fixup commits, and then re-order them, or (2) mark points in your
>> history as 'edit', and rewrite them in a detached state, and I'm sure
>> many more).
>> I'm curious if you or anyone else has thought about how this might work
>> in Git.
> I've wanted a "git absorb" for a while, but have done no actual work on
> it, I just found out about it.
> I think a combination of these two heuristics would probably do the
> trick:
>  1. If a change in your "git diff" output has a hunk whose lines overlap
>     with an earlier commit in the @{u}.. range, we do the equivalent of
>     "git add -p", select that hunk, and "git commit --fixup <that
>     commit>". We fixup the most recent commit that matches (otherwise
>     commit>we'd conflict).
>  2. Have some mode where we fall back from #1 and consider changes to
>     entire files, if that's unambiguous.
> The neat thing about this would be that you could tweak how promiscuous
> #1 would be via the -U option to git-diff, and #2 would just be a
> special case of -U9999999999999 (we should really add a -Uinf...).
> Then once you ran this you could run "git rebase -i --autosquash" to see
> how the TODO list would look, and optionally have some "git absorb
> --now" or whatever to do the "git add -p", "git commit --fixup" and "git
> rebase --autosquash" all in one go.
>> [1]: http://files.lihdd.net/hgabsorb-note.pdf