Re: Fwd: Idea: add --squash to cherry-pick

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 11, 2022, 16:43 UTC
Message-ID: <xmqqzggag28x.fsf@gitster.g>
In-Reply-To: <a4c937ed-ea89-0564-db64-f0634fe7eeee@kdbg.org>

Johannes Sixt <j6t@kdbg.org> writes:

Show 8 quoted lines

> That question on Stackoverflow asks "how to do X with Y". But Y (git
> cherry-pick) is the wrong tool to do X (apply commits from a branch to
> somewhere else in squashed form).
>
>    git diff A...B | git apply --3way
>
> would do what you want. You would have to come up with a new commit
> message anyway, so cherry-pick would be of little use there.

I do agree that cherry-pick is not the best solution for that XY problem, but in a typical undisciplined development work, it is not entirely implausible that pieces from original commit message may still be of some use, exactly the same way as people would want to use "squash" while "rebase -i". Most commits may have completely unusable "oops fix", "worked more", etc. messages, but some of them may summarize what the past handful steps with such garbage messages have done, which may be worth salvaging.

If I were solving the XY problem, I would probably use "rebase -i".

To transplant the range A..B of the history on top of HEAD, for example, I'd start with (notice ^0 after B, as I do not trust myself so I'd leave the true branch B untouched as I may make mistakes while running rebase):

    $ git checkout --detach HEAD	;# this is only to use @{-1} later
    $ git rebase -i --onto HEAD A B^0

Then if my goal is to squash everything down into a single commit, then replace all 'pick', except for the first one, to 'squash'. That will give me one single chance to edit a single commit message, but the editor buffer starts with the log message from all of the original, so I can pick good bits from them while writing new stuf.

I'll have the result on detached HEAD. If I like the result, I may update the branch I was originally on with it.

    $ git checkout -B @{-1}

Or, if I don't, perhaps because I made mistakes, then I can just discard it and go back to the original branch.

    $ git checkout @{-1}