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From: Eugeniu Rosca <erosca@de.adit-jv.com>
To: "Elijah Newren" <newren@gmail.com>,
	"SZEDER Gábor" <szeder.dev@gmail.com>
Cc: "Eugeniu Rosca" <erosca@de.adit-jv.com>,
	"Junio C Hamano" <gitster@pobox.com>, "Jeff King" <peff@peff.net>,
	"Ævar Arnfjörð" <avarab@gmail.com>,
	"Git Mailing List" <git@vger.kernel.org>,
	"Eugeniu Rosca" <roscaeugeniu@gmail.com>
Subject: Re: Unreliable 'git rebase --onto'
Date: Thu, 9 Jan 2020 11:53:07 +0100
Message-ID: <20200109105307.GA1349@lxhi-065.adit-jv.com> (raw)
In-Reply-To: <CABPp-BHsyMOz+hi7EYoAnAWfzms7FRfwqCoarnu8H+vyDoN6SQ@mail.gmail.com>

Hi Elijah, hi Szeder,

On Wed, Jan 08, 2020 at 02:06:22PM -0800, Elijah Newren wrote:
> This looks like a known bug in rebase, in particular in the am-backend that
> rebase uses by default.  If I'm correct that it's just a context region
> issue, then this is the same bug that was recently discussed at
> https://lore.kernel.org/git/CAN_72e2h2avv-U9BVBYqXVKiC+5kHy-pjejyMSD3X22uRXE39g@mail.gmail.com/.
> The current plan is to switch the default over to the merge backend (the
> same machinery that cherry-pick uses), which doesn't suffer from the same
> shortcomings (you can see the current work being done in this area at
> https://lore.kernel.org/git/pull.679.v3.git.git.1577217299.gitgitgadget@gmail.com/
> ).

Thank you for your feedback and references, here and in [*].

Once hit by this or similar issues, I think there is high chance for
people to go through the same feelings as described by Pavel in [**]:

  ---
  That's so scary that I'm going to stop using "git rebase" for now.
  ---

Some years ago I was hit by 'git merge' producing slightly different
results compared to 'git rebase --onto' and 'git cherry-pick A..B'
(maybe I can come up with a reproduction scenario for that too).

Since then, I usually contrast the outcomes of merging, cherry-picking
and rebasing, to make sure they match, but that's painful and
time-consuming.

> In the mean time, you can pass the -m flag to rebase to avoid these types
> of problems.  In fact, if you could retry with -m you may be able to
> confirm whether it's the same issue.

Indeed, neither `git rebase -m` nor `git rebase -i` exhibit the problem.

[*] https://lore.kernel.org/git/CABPp-BHsy75UGm4wTOP2_AYik_dZi-_BxtAn-hyi-ZrNRRWGuw@mail.gmail.com/T/#m1cbf80ef56c260a626146d61291d7fbabd108f1b
[**] https://lore.kernel.org/git/CAN_72e2h2avv-U9BVBYqXVKiC+5kHy-pjejyMSD3X22uRXE39g@mail.gmail.com/

Thanks again.

-- 
Best Regards,
Eugeniu

  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-08 21:43 Eugeniu Rosca
2020-01-08 22:35 ` SZEDER Gábor
2020-01-09  0:55   ` Elijah Newren
2020-01-09 15:03     ` SZEDER Gábor
2020-01-09 17:53       ` Elijah Newren
2020-01-21 19:18       ` [PATCH v1] rebase -i: stop checking out the tip of the branch to rebase Alban Gruin
2020-01-21 20:07         ` Elijah Newren
2020-01-22 20:24         ` Junio C Hamano
2020-01-22 20:47         ` Junio C Hamano
2020-01-24 14:45           ` Alban Gruin
2020-01-24 14:45         ` [PATCH v2] " Alban Gruin
2020-01-24 14:55           ` Alban Gruin
2020-01-24 18:12             ` Junio C Hamano
2020-01-24 15:05           ` [PATCH v3] " Alban Gruin
2020-01-24 18:30             ` Junio C Hamano
2020-02-05 14:31             ` Johannes Schindelin
2020-01-24 17:11           ` [PATCH v2] " Andrei Rybak
2020-01-09 11:13   ` Unreliable 'git rebase --onto' Eugeniu Rosca
     [not found] ` <CABPp-BHsyMOz+hi7EYoAnAWfzms7FRfwqCoarnu8H+vyDoN6SQ@mail.gmail.com>
2020-01-09 10:53   ` Eugeniu Rosca [this message]
2020-01-09 18:05     ` Elijah Newren
2020-01-10  0:06       ` Eugeniu Rosca
2020-01-10  2:35         ` Elijah Newren

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