From: Sergey Organov <sorganov@gmail.com>
To: Igor Djordjevic <igor.d.djordjevic@gmail.com>
Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de>,
Phillip Wood <phillip.wood@dunelm.org.uk>,
Jacob Keller <jacob.keller@gmail.com>,
Git Mailing List <git@vger.kernel.org>,
Johannes Sixt <j6t@kdbg.org>, Junio C Hamano <gitster@pobox.com>
Subject: Re: [RFC] Rebasing merges: a jorney to the ultimate solution(RoadClear)
Date: Tue, 20 Mar 2018 17:43:04 +0300 [thread overview]
Message-ID: <87r2oevmdj.fsf@javad.com> (raw)
In-Reply-To: <34e8d563-a035-b09e-e959-748f2b4f4b99@gmail.com> (Igor Djordjevic's message of "Mon, 19 Mar 2018 22:35:09 +0100")
Igor Djordjevic <igor.d.djordjevic@gmail.com> writes:
> Hi Sergey,
>
> On 19/03/2018 06:44, Sergey Organov wrote:
>>
>> > > > > > Second side note: if we can fast-forward, currently we prefer
>> > > > > > that, and I think we should keep that behavior with -R, too.
>> > > > >
>> > > > > I agree.
>> > > >
>> > > > I'm admittedly somewhat lost in the discussion, but are you
>> > > > talking fast-forward on _rebasing_ existing merge? Where would it
>> > > > go in any of the suggested algorithms of rebasing and why?
>> > > >
>> > > > I readily see how it can break merges. E.g., any "git merge
>> > > > --ff-only --no-ff" merge will magically disappear. So, even if
>> > > > somehow supported, fast-forward should not be performed by default
>> > > > during _rebasing_ of a merge.
>> > >
>> > > Hmm, now that you brought this up, I can only agree, of course.
>> > >
>> > > What I had in my mind was more similar to "no-rebase-cousins", like
>> > > if we can get away without actually rebasing the merge but still
>> > > using the original one, do it. But I guess that`s not what Johannes
>> > > originally asked about.
>> > >
>> > > This is another definitive difference between rebasing (`pick`?) and
>> > > recreating (`merge`) a merge commit - in the case where we`re rebasing,
>> > > of course it doesn`t make sense to drop commit this time (due to
>> > > fast-forward). This does make sense in recreating the merge (only).
>> >
>> > Eh, I might take this back. I think my original interpretation (and
>> > agreement) to fast-forwarding is correct.
>> >
>> > But the confusion here comes from `--no-ff` as used for merging, as
>> > opposed to `--no-ff` as used for rebasing. I _think_ Johannes meant
>> > the latter one.
>> >
>> > In rebasing, `--no-ff` means that even if a commit inside todo list
>> > isn`t to be changed, do not reuse it but create a new one. Here`s
>> > excerpt from the docs[1]:
>> >
>> > --no-ff
>> > With --interactive, cherry-pick all rebased commits instead of
>> > fast-forwarding over the unchanged ones. This ensures that the
>> > entire history of the rebased branch is composed of new commits.
>> >
>> > Without --interactive, this is a synonym for --force-rebase.
>> >
>> >
>> > So fast-forwarding in case of rebasing (merge commits as well) is
>> > something you would want by default, as it wouldn`t drop/lose
>> > anything, but merely reuse existing commit (if unchanged), instead of
>> > cherry-picking (rebasing) it into a new (merge) commit anyway.
>>
>> This sounds like breakage. E.g., it seems to be breaking every "-x ours"
>> merge out there.
>
> Either you are not understanding how rebase fast-forward works, or
> I`m missing what you are pointing to... Mind explaining how can
> something that`s left unchanged suddenly become a breakage?
It was misunderstanding on my side indeed, sorry.
>
>> Fast-forwarding existing merge, one way or another, still seems to be
>> wrong idea to me, as merge commit is not only about content change, but
>> also about joint point at particular place in the DAG.
>
> Not sure what this has to do with rebase fast-forwarding, either -
> nothing changes for fast-forwarded (merge or non-merge) commit in
> question, both content, joint point and everything else stays exactly
> the same. If anything changed, then it can`t/won`t be fast-forwarded,
> being unchanged is a prerequisite.
>
> Let me elaborate a bit. Here`s a starting diagram:
[... detailed explanation skipped for brevity ...]
> Does this settle your concerns, or I`m missing something?
Yes, it does, thank you! Leaving as many leading commits as possible
unchanged during rebase is what fast-forward mean in this case then, and
it's pretty OK with me.
>> As for fast-forwarding re-merge, explicitly requested, I'm not sure. On
>> one hand, it's inline with the default "git merge" behavior, on the
>> other hand, it still feels wrong, somehow.
>
> Regarding fast-forwarding in context of merging, in case where we are
> recreating merges (not rebasing them), following existing `git merge`
> logic might make sense, where I would expect rebasing todo list `merge`
> command to pick-up tricks from `git merge` as needed, like learning
> to accept `--no-ff` option, for example, thus not fast-forwarding
> merges (on request) even when possible.
>
> Though, I do agree that in case you want to recreate an existing merge
> (instead of just rebasing it), `merge` command fast-forwarding might
> probably not be what you want for the most of the time, but I`m afraid
> having rebase todo list `merge` command default behavior different than
> `git merge` default one (in regards to fast-forwarding) would be
> confusing... or not?
>
> From what I could grasp so far, usually Git commands` default
> behavior is (explained to be) chosen per "most common use case", so
> might be non fast-forwarding would be fine as default for rebase todo
> list `merge` command, even though different than `git merge`
> itself...?
As far as I can tell, fast-forward as default for "git merge" has been
chosen to avoid excessive unintended merges in typical workflows, and
therefore this decision is not actually applicable to rebasing, I think.
I'm inclined to disable merges to fast-forward during history rebasing,
at least by default.
As far as I can tell, current "--preserve-merges" does fast-forward and
breaks "git merge --ff-only --no-ff" merges, among other things it
breaks, and that was my primary concern here. Didn't check
what "--recreate-merges" does though.
-- Sergey
next prev parent reply other threads:[~2018-03-20 14:43 UTC|newest]
Thread overview: 173+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-16 13:08 [RFC] Rebasing merges: a jorney to the ultimate solution (Road Clear) Sergey Organov
2018-02-18 4:16 ` Jacob Keller
2018-02-19 5:28 ` Sergey Organov
2018-02-19 23:44 ` Igor Djordjevic
2018-02-20 12:42 ` Sergey Organov
2018-02-27 0:07 ` Johannes Schindelin
2018-02-27 5:01 ` Sergey Organov
2018-02-27 5:30 ` Jacob Keller
2018-02-27 16:21 ` Johannes Schindelin
2018-02-27 18:55 ` Igor Djordjevic
2018-02-27 19:59 ` Igor Djordjevic
2018-02-27 23:27 ` Johannes Schindelin
2018-02-28 2:12 ` Igor Djordjevic
2018-02-28 4:35 ` Igor Djordjevic
2018-02-28 6:14 ` Sergey Organov
2018-02-28 20:53 ` Igor Djordjevic
2018-02-28 5:44 ` Sergey Organov
2018-02-28 19:42 ` Igor Djordjevic
2018-02-27 23:40 ` Igor Djordjevic
2018-02-28 0:10 ` Junio C Hamano
2018-02-28 2:35 ` Igor Djordjevic
2018-02-28 5:27 ` Sergey Organov
2018-02-28 0:36 ` Jacob Keller
2018-02-28 1:33 ` Igor Djordjevic
2018-02-28 1:43 ` Igor Djordjevic
2018-02-28 5:21 ` Sergey Organov
2018-02-28 19:09 ` Igor Djordjevic
2018-03-01 5:27 ` Sergey Organov
2018-02-28 5:19 ` Sergey Organov
2018-02-28 20:25 ` Igor Djordjevic
2018-02-28 22:17 ` Igor Djordjevic
2018-03-01 5:19 ` Sergey Organov
2018-03-01 5:39 ` Sergey Organov
2018-03-02 1:16 ` Igor Djordjevic
2018-03-02 5:40 ` Sergey Organov
2018-03-02 17:45 ` Igor Djordjevic
2018-03-02 11:17 ` [RFC] Rebasing merges: a jorney to the ultimate solution(RoadClear) Phillip Wood
2018-03-02 12:36 ` Phillip Wood
2018-03-02 16:02 ` Jacob Keller
2018-03-02 23:33 ` Igor Djordjevic
2018-03-06 10:36 ` Phillip Wood
2018-03-06 18:12 ` Johannes Schindelin
2018-03-06 19:43 ` Igor Djordjevic
2018-03-07 7:26 ` Johannes Schindelin
2018-03-08 11:20 ` Phillip Wood
2018-03-08 12:16 ` Phillip Wood
2018-03-08 16:05 ` Igor Djordjevic
2018-03-11 12:00 ` Johannes Schindelin
2018-03-11 16:33 ` Igor Djordjevic
2018-03-12 10:37 ` Johannes Schindelin
2018-03-12 12:56 ` Sergey Organov
2018-03-13 0:01 ` Igor Djordjevic
2018-03-26 12:03 ` Johannes Schindelin
2018-03-27 5:08 ` Sergey Organov
2018-03-27 13:35 ` Johannes Schindelin
2018-04-02 6:07 ` Sergey Organov
2018-03-12 23:54 ` Igor Djordjevic
2018-03-13 6:25 ` Sergey Organov
2018-03-08 15:56 ` Igor Djordjevic
2018-03-11 12:08 ` Johannes Schindelin
2018-03-11 17:34 ` Igor Djordjevic
2018-03-12 10:46 ` Johannes Schindelin
2018-03-13 0:16 ` Igor Djordjevic
2018-03-26 13:07 ` Johannes Schindelin
2018-03-27 5:51 ` Sergey Organov
2018-03-27 13:49 ` Johannes Schindelin
2018-03-28 5:57 ` Sergey Organov
2018-03-30 13:41 ` Johannes Schindelin
2018-03-30 16:36 ` Sergey Organov
2018-03-28 5:57 ` Sergey Organov
[not found] ` <CA+P7+xoDQ2mzhxeZPFhaY+TaSoKkQm=5AtoduHH06-VggOJ2jg@mail.gmail.com>
2018-03-28 11:29 ` Sergey Organov
[not found] ` <CA+P7+xo19mHrWz9Fy-ifgCcVJM2xwzcLj7F2NvFe2LwGbaJiDQ@mail.gmail.com>
2018-03-29 5:53 ` Sergey Organov
2018-03-30 10:38 ` Johannes Schindelin
2018-03-30 12:36 ` Sergey Organov
2018-03-30 13:33 ` Johannes Schindelin
2018-03-30 15:13 ` Sergey Organov
2018-03-28 12:10 ` Sergey Organov
2018-03-08 16:07 ` Jacob Keller
2018-03-11 12:11 ` Johannes Schindelin
2018-03-11 17:46 ` Igor Djordjevic
2018-03-08 15:16 ` Igor Djordjevic
2018-03-08 16:21 ` Igor Djordjevic
2018-03-11 12:22 ` Johannes Schindelin
2018-03-14 14:24 ` Sergey Organov
2018-03-14 23:11 ` Igor Djordjevic
2018-03-15 6:00 ` Sergey Organov
2018-03-15 21:51 ` Igor Djordjevic
2018-03-17 2:08 ` Igor Djordjevic
2018-03-19 5:44 ` Sergey Organov
2018-03-19 21:35 ` Igor Djordjevic
2018-03-20 14:43 ` Sergey Organov [this message]
2018-03-26 13:47 ` Johannes Schindelin
2018-03-06 23:24 ` Junio C Hamano
2018-03-07 7:09 ` Johannes Schindelin
2018-03-07 18:20 ` Junio C Hamano
2018-03-08 7:03 ` Johannes Schindelin
2018-03-08 8:11 ` Junio C Hamano
2018-03-09 17:09 ` Johannes Schindelin
2018-03-02 16:00 ` Jacob Keller
2018-03-02 18:14 ` Igor Djordjevic
2018-03-03 17:29 ` Igor Djordjevic
2018-03-05 5:35 ` Sergey Organov
2018-03-02 11:31 ` [RFC] Rebasing merges: a jorney to the ultimate solution (Road Clear) Phillip Wood
2018-03-03 0:29 ` Igor Djordjevic
2018-03-05 5:00 ` Sergey Organov
2018-03-06 10:52 ` Phillip Wood
2018-03-06 16:56 ` Junio C Hamano
2018-03-08 7:05 ` Johannes Schindelin
2018-03-08 8:18 ` Junio C Hamano
2018-03-11 11:56 ` Johannes Schindelin
2018-03-13 18:24 ` Junio C Hamano
2018-03-26 13:17 ` Johannes Schindelin
2018-03-05 17:29 ` Johannes Schindelin
2018-03-06 23:21 ` Igor Djordjevic
2018-03-07 7:04 ` Johannes Schindelin
2018-03-06 10:45 ` Phillip Wood
2018-03-06 11:45 ` Sergey Organov
2018-03-08 16:30 ` Igor Djordjevic
2018-03-06 18:12 ` Johannes Schindelin
2018-03-07 5:08 ` Sergey Organov
2018-03-07 6:58 ` Johannes Schindelin
2018-03-07 14:34 ` Sergey Organov
2018-03-08 6:45 ` Johannes Schindelin
2018-03-12 12:31 ` Sergey Organov
2018-03-26 11:37 ` Johannes Schindelin
2018-03-27 5:11 ` Sergey Organov
2018-03-27 12:55 ` Johannes Schindelin
2018-03-28 4:32 ` Sergey Organov
2018-03-08 11:08 ` Phillip Wood
2018-03-05 17:52 ` Johannes Schindelin
2018-03-13 16:10 ` Sergey Organov
2018-03-14 1:12 ` Igor Djordjevic
2018-03-14 7:21 ` Sergey Organov
2018-03-15 0:09 ` Igor Djordjevic
2018-03-15 7:52 ` Sergey Organov
2018-03-15 23:08 ` Igor Djordjevic
2018-03-16 7:31 ` Sergey Organov
2018-03-17 3:04 ` Igor Djordjevic
2018-03-19 6:01 ` Sergey Organov
2018-03-26 14:11 ` Johannes Schindelin
2018-02-28 0:29 ` Jacob Keller
2018-02-27 11:57 ` Sergey Organov
2018-02-27 18:14 ` Junio C Hamano
2018-02-28 0:30 ` Jacob Keller
2018-02-28 5:54 ` Sergey Organov
2018-02-28 4:53 ` Sergey Organov
2018-03-06 13:26 ` [RFC v2] " Sergey Organov
2018-03-07 6:46 ` Johannes Schindelin
2018-03-07 13:27 ` Sergey Organov
2018-03-07 14:08 ` Johannes Schindelin
2018-03-07 15:16 ` Sergey Organov
2018-03-08 7:01 ` Johannes Schindelin
2018-03-12 12:42 ` Sergey Organov
2018-03-26 11:50 ` Johannes Schindelin
2018-03-08 19:58 ` Igor Djordjevic
2018-03-08 20:27 ` Igor Djordjevic
2018-03-08 22:05 ` Igor Djordjevic
2018-03-08 23:31 ` Igor Djordjevic
2018-03-11 15:47 ` Johannes Schindelin
2018-03-11 20:53 ` Igor Djordjevic
2018-03-12 10:20 ` Johannes Schindelin
2018-03-12 13:49 ` Sergey Organov
2018-03-26 12:44 ` Johannes Schindelin
2018-03-27 5:32 ` Sergey Organov
2018-03-13 0:29 ` Igor Djordjevic
2018-03-26 13:58 ` Johannes Schindelin
2018-03-12 13:07 ` Sergey Organov
2018-03-11 15:40 ` Johannes Schindelin
2018-03-11 22:04 ` Igor Djordjevic
2018-03-12 12:05 ` Sergey Organov
2018-03-26 11:33 ` Johannes Schindelin
2018-03-27 5:34 ` Sergey Organov
2018-03-12 22:41 ` Igor Djordjevic
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