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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Denton Liu <liu.denton@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
	Eric Sunshine <sunshine@sunshineco.com>,
	Junio C Hamano <gitster@pobox.com>,
	Johannes Schindelin <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH v3 0/4] rebase: teach rebase --keep-base
Date: Sat, 13 Apr 2019 23:10:43 +0200	[thread overview]
Message-ID: <8736mlfw6k.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <20190406203800.GA6147@archbookpro.localdomain>


On Sat, Apr 06 2019, Denton Liu wrote:

> On Sat, Apr 06, 2019 at 09:44:49PM +0200, Ævar Arnfjörð Bjarmason wrote:
>>
>> On Mon, Apr 01 2019, Denton Liu wrote:
>>
>> > Thanks again for your feedback, Ævar! I think we're both on the same page now.
>> > Hopefully I've addressed all of your high-level concerns with this patchset and
>> > we can move into a discussion on implementation detail.
>>
>> Late in replying to this, have been off-list. This also applies for your
>> v4.
>>
>> The current version you have still doesn't explain the "Why would we
>> redundantly rebase every time in this case..." question I had in
>> https://public-inbox.org/git/87tvfma8yt.fsf@evledraar.gmail.com/
>>
>> I *think* it's closer to "it was easier to implement this in terms of
>> --onto, which happens to behave that way now" than "it must work this
>> way for --keep-base", which is fair enough.
>
> Correct, the reason why --keep-base was not lazy initially was because
> "--onto did it that way". You are correct in that --keep-base should be
> lazily rebasing so I changed --onto's behaviour in 3/4 because it would
> also benefit from laziness. Thus, now --keep-base lazily rebases because
> --onto also does.
>
>>
>> Although I see when I forward-port my POC patch from that E-Mail that
>> one test fails now, which is good, that wasn't the case before, but it
>> looks like that might be testing something else than just the lazy
>> behavior.
>
> The test fails because the patch disables fork_point if --keep-base is
> set. So, with the patch applied, C is rebased even though it is excluded
> when fork_point is set.
>
>>
>> It would be good to know in terms of commit message or (better) explicit
>> tests so that if we teach these various rebase modes the same lazyness
>> --fork-point uses in the future it's clear if that's OK or not.
>
> Sorry, could you please clarify what you mean by the "lazyness
> --fork-point uses"? I don't understand what laziness is introduced by
> using --fork-point. Also, are the tests in t3432 not sufficient for
> testing fast-forwarding (aka lazy) behaviour?

Late reply, sorry. I mean if I do e.g. on git.git:

    git checkout -b avar/test 041f5ea1cf

I.e. branch of Junio's "The third batch" (we're now on the 4th) and
then:

    git branch --set-upstream-to origin/master

And commit a dummy change, I'm now:

    On branch avar/test
    Your branch and 'origin/master' have diverged,
    and have 1 and 33 different commits each, respectively.

Then I run a --keep-base rebase twice:

    $ git log --oneline --no-decorate -2; ~/g/git/git --exec-path=$PWD rebase --keep-base; git rev-parse HEAD
    fc3e916c5f foo
    041f5ea1cf The third batch
    First, rewinding head to replay your work on top of it...
    Applying: foo
    b10e672074dfee6b6e8b2901c9bb49f856a13708
    $ git log --oneline --no-decorate -2; ~/g/git/git --exec-path=$PWD rebase --keep-base; git rev-parse HEAD
    b10e672074 foo
    041f5ea1cf The third batch
    First, rewinding head to replay your work on top of it...
    Applying: foo
    fd3029e73b89f5a799653ff17199d00f2a6ee2e2

I.e. I'll keep on getting a new commit, even though by any criteria I
can think of for this type of case there's no work to do. I.e. we're
already based on 041f5ea1cf, no need to rebase again.

Of course this is also currently the case with --fork-point without
argument, which'll settle on (note fourth, not third):

    $ git log --oneline --no-decorate -2; ~/g/git/git --exec-path=$PWD rebase --fork-point; git rev-parse HEAD
    85a1861cec foo
    e35b8cb8e2 The fourth batch
    First, rewinding head to replay your work on top of it...
    Applying: foo
    c6046e97af29d71bf6270080acf188c095e0cb7c
    $ git log --oneline --no-decorate -2; ~/g/git/git --exec-path=$PWD rebase --fork-point; git rev-parse HEAD
    c6046e97af foo
    e35b8cb8e2 The fourth batch
    First, rewinding head to replay your work on top of it...
    Applying: foo
    672d22d58e9aa9b6a28054531c21e1f1b598b013

Whereas a --keep-base in *this* case should be identical to:

    $ git log --oneline --no-decorate -2; ~/g/git/git --exec-path=$PWD rebase $(git merge-base --fork-point origin/master HEAD); git rev-parse HEAD
    fc3e916c5f foo
    041f5ea1cf The third batch
    Current branch avar/test is up to date.
    fc3e916c5fc707cfc83f28b3faca81046306b305

The reason I'm asking is that as noted in the thread starting at
https://public-inbox.org/git/20190224101029.GA13438@sigill.intra.peff.net/
we used to in *some* cases do the same for:

    rebase $(git merge-base --fork-point origin/master HEAD)

As for just:

    rebase --fork-point

I.e. say "Current branch is up-to-date". I'm planning to loop back to
that and fix it for the --fork-point case. So I was wondering if you
could think of a reason for why --keep-base couldn't also do the same,
or if there was some intrinsic difference I'm missing.

Anyway. Don't worry about it. When I poke at it it'll likely shake out
of the respective tests.

I was just wondering if you having looked at many of the same things
recently could understand my ramblings and knew if this was a case of
"yup, we could add a bit more to that can_fast_forward(...) case and
make it lazy too", or "no, --keep-base is special for reasons you're
missing...".

      reply	other threads:[~2019-04-13 21:10 UTC|newest]

Thread overview: 123+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-23 15:25 [PATCH 0/3] rebase: learn --keep-base Denton Liu
2019-03-23 15:25 ` [PATCH 1/3] rebase: teach rebase --keep-base Denton Liu
2019-03-24  3:46   ` Eric Sunshine
2019-03-24 13:20   ` Junio C Hamano
2019-03-25  0:06     ` Denton Liu
2019-03-25  5:41       ` Denton Liu
2019-04-01 10:45         ` Junio C Hamano
2019-03-24 13:37   ` Junio C Hamano
2019-03-25  5:47   ` Denton Liu
2019-03-25 18:50   ` Johannes Schindelin
2019-03-25 19:29     ` Denton Liu
2019-03-26 13:27       ` Johannes Schindelin
2019-03-23 15:25 ` [PATCH 2/3] t3416: test " Denton Liu
2019-03-23 15:25 ` [PATCH 3/3] git-rebase.txt: document --keep-base option Denton Liu
2019-03-24 13:15 ` [PATCH 0/3] rebase: learn --keep-base Junio C Hamano
2019-03-25  0:04   ` Denton Liu
2019-04-01 10:45     ` Junio C Hamano
2019-03-26 14:35 ` Ævar Arnfjörð Bjarmason
2019-03-26 17:50   ` Denton Liu
2019-03-26 20:35     ` Ævar Arnfjörð Bjarmason
2019-03-26 21:30       ` Denton Liu
2019-03-27 15:39         ` Ævar Arnfjörð Bjarmason
2019-03-28 22:17 ` [PATCH v2] rebase: teach rebase --keep-base Denton Liu
2019-03-28 23:13   ` Ævar Arnfjörð Bjarmason
2019-03-29 15:47   ` Johannes Schindelin
2019-03-29 17:52     ` Denton Liu
2019-04-01 10:46     ` Junio C Hamano
2019-04-01 20:51   ` [PATCH v3 0/4] " Denton Liu
2019-04-01 20:51     ` [PATCH v3 1/4] t3431: add rebase --fork-point tests Denton Liu
2019-04-04 20:28       ` Denton Liu
2019-04-05 11:15       ` SZEDER Gábor
2019-04-08  4:38         ` Junio C Hamano
2019-04-05 14:55       ` Johannes Schindelin
2019-04-05 17:25         ` Denton Liu
2019-04-05 17:51           ` Johannes Sixt
2019-04-05 18:51             ` Johannes Schindelin
2019-04-05 20:19               ` Johannes Schindelin
2019-04-05 21:10                 ` SZEDER Gábor
2019-04-01 20:51     ` [PATCH v3 2/4] t3432: test rebase fast-forward behavior Denton Liu
2019-04-01 20:52     ` [PATCH v3 3/4] rebase: fast-forward --onto in more cases Denton Liu
2019-04-02  1:25       ` Junio C Hamano
2019-04-02  1:48         ` Junio C Hamano
2019-04-02  4:44           ` Denton Liu
2019-04-01 20:52     ` [PATCH v3 4/4] rebase: teach rebase --keep-base Denton Liu
2019-04-05 21:39     ` [PATCH v4 0/4] " Denton Liu
2019-04-05 21:40       ` [PATCH v4 1/4] t3431: add rebase --fork-point tests Denton Liu
2019-04-05 21:40       ` [PATCH v4 2/4] t3432: test rebase fast-forward behavior Denton Liu
2019-04-05 21:40       ` [PATCH v4 3/4] rebase: fast-forward --onto in more cases Denton Liu
2019-04-05 21:40       ` [PATCH v4 4/4] rebase: teach rebase --keep-base Denton Liu
2019-04-15 22:29       ` [PATCH v5 0/5] " Denton Liu
2019-04-15 22:29         ` [PATCH v5 1/5] t3431: add rebase --fork-point tests Denton Liu
2019-04-15 22:29         ` [PATCH v5 2/5] t3432: test rebase fast-forward behavior Denton Liu
2019-04-15 22:29         ` [PATCH v5 3/5] rebase: fast-forward --onto in more cases Denton Liu
2019-04-16  6:26           ` Junio C Hamano
2019-04-16 13:59           ` Phillip Wood
2019-04-17  6:44             ` Denton Liu
2019-04-17 14:14               ` Phillip Wood
2019-04-19 17:08           ` Denton Liu
2019-04-15 22:29         ` [PATCH v5 4/5] rebase: fast-forward --fork-point " Denton Liu
2019-04-15 22:29         ` [PATCH v5 5/5] rebase: teach rebase --keep-base Denton Liu
2019-04-17 18:01       ` [PATCH v6 0/5] " Denton Liu
2019-04-17 18:01         ` [PATCH v6 1/6] t3431: add rebase --fork-point tests Denton Liu
2019-04-17 18:01         ` [PATCH v6 2/6] t3432: test rebase fast-forward behavior Denton Liu
2019-04-17 18:01         ` [PATCH v6 3/6] rebase: refactor can_fast_forward into goto tower Denton Liu
2019-04-17 18:01         ` [PATCH v6 4/6] rebase: fast-forward --onto in more cases Denton Liu
2019-04-17 19:59           ` Phillip Wood
2019-04-17 18:01         ` [PATCH v6 5/6] rebase: fast-forward --fork-point " Denton Liu
2019-04-17 18:01         ` [PATCH v6 6/6] rebase: teach rebase --keep-base Denton Liu
2019-04-21  8:11         ` [PATCH v7 0/6] rebase: learn --keep-base Denton Liu
2019-04-21  8:11           ` [PATCH v7 1/6] t3431: add rebase --fork-point tests Denton Liu
2019-04-23 23:12             ` Denton Liu
2019-04-21  8:11           ` [PATCH v7 2/6] t3432: test rebase fast-forward behavior Denton Liu
2019-04-21  8:11           ` [PATCH v7 3/6] rebase: refactor can_fast_forward into goto tower Denton Liu
2019-04-21  8:11           ` [PATCH v7 4/6] rebase: fast-forward --onto in more cases Denton Liu
2019-04-21  8:11           ` [PATCH v7 5/6] rebase: fast-forward --fork-point " Denton Liu
2019-04-21  8:11           ` [PATCH v7 6/6] rebase: teach rebase --keep-base Denton Liu
2019-05-08  0:12           ` [RFC WIP PATCH v8 00/13] learn --keep-base & more Ævar Arnfjörð Bjarmason
2019-05-08  3:57             ` Junio C Hamano
2019-07-19 19:14               ` Junio C Hamano
2019-07-19 21:01                 ` Denton Liu
2019-08-25  9:11             ` [PATCH v9 0/9] rebase: learn --keep-base and improvements on fast-forward behaviour Denton Liu
2019-08-25  9:11               ` [PATCH v9 1/9] t3431: add rebase --fork-point tests Denton Liu
2019-08-25  9:12               ` [PATCH v9 2/9] t3432: test rebase fast-forward behavior Denton Liu
2019-08-25  9:12               ` [PATCH v9 3/9] t3432: distinguish "noop-same" v.s. "work-same" in "same head" tests Denton Liu
2019-08-25  9:12               ` [PATCH v9 4/9] t3432: test for --no-ff's interaction with fast-forward Denton Liu
2019-08-25  9:12               ` [PATCH v9 5/9] rebase: refactor can_fast_forward into goto tower Denton Liu
2019-08-25 13:17                 ` Pratyush Yadav
2019-08-26 23:17                   ` Denton Liu
2019-08-25  9:12               ` [PATCH v9 6/9] rebase: fast-forward --onto in more cases Denton Liu
2019-08-25  9:12               ` [PATCH v9 7/9] rebase: fast-forward --fork-point " Denton Liu
2019-08-25  9:12               ` [PATCH v9 8/9] rebase tests: test linear branch topology Denton Liu
2019-08-25  9:12               ` [PATCH v9 9/9] rebase: teach rebase --keep-base Denton Liu
2019-08-25 22:59                 ` Philip Oakley
2019-08-26 19:37               ` [PATCH v9 0/9] rebase: learn --keep-base and improvements on fast-forward behaviour Junio C Hamano
2019-08-27  5:37               ` [PATCH v10 " Denton Liu
2019-08-27  5:37                 ` [PATCH v10 1/9] t3431: add rebase --fork-point tests Denton Liu
2019-08-27  5:37                 ` [PATCH v10 2/9] t3432: test rebase fast-forward behavior Denton Liu
2019-08-27  5:37                 ` [PATCH v10 3/9] t3432: distinguish "noop-same" v.s. "work-same" in "same head" tests Denton Liu
2019-08-27  5:37                 ` [PATCH v10 4/9] t3432: test for --no-ff's interaction with fast-forward Denton Liu
2019-08-27  8:11                   ` SZEDER Gábor
2019-08-27  5:37                 ` [PATCH v10 5/9] rebase: refactor can_fast_forward into goto tower Denton Liu
2019-08-27  5:37                 ` [PATCH v10 6/9] rebase: fast-forward --onto in more cases Denton Liu
2019-08-27  5:38                 ` [PATCH v10 7/9] rebase: fast-forward --fork-point " Denton Liu
2019-08-27  5:38                 ` [PATCH v10 8/9] rebase tests: test linear branch topology Denton Liu
2019-08-27  5:38                 ` [PATCH v10 9/9] rebase: teach rebase --keep-base Denton Liu
2019-05-08  0:12           ` [RFC WIP PATCH v8 01/13] t3431: add rebase --fork-point tests Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 02/13] t3432: test rebase fast-forward behavior Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 03/13] t3432: distinguish "noop-same" v.s. "work-same" in "same head" tests Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 04/13] t3432: test for --no-ff's interaction with fast-forward Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 05/13] rebase: refactor can_fast_forward into goto tower Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 06/13] rebase: fast-forward --onto in more cases Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 07/13] rebase: fast-forward --fork-point " Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 08/13] rebase: teach rebase --keep-base Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 09/13] rebase tests: test linear branch topology Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 10/13] rebase: don't rebase linear topology with --fork-point Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 11/13] rebase: eliminate side-effects from can_fast_forward() Ævar Arnfjörð Bjarmason
2019-05-17 21:16             ` Johannes Schindelin
2019-05-08  0:12           ` [RFC WIP PATCH v8 12/13] rebase: add a should_fast_forward() utility function Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 13/13] WIP: can_fast_forward() support for --preserve-merges and --rebase-merges Ævar Arnfjörð Bjarmason
2019-05-17 22:02             ` Johannes Schindelin
2019-04-06 19:44     ` [PATCH v3 0/4] rebase: teach rebase --keep-base Ævar Arnfjörð Bjarmason
2019-04-06 20:38       ` Denton Liu
2019-04-13 21:10         ` Ævar Arnfjörð Bjarmason [this message]

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