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From: Jonathan Nieder <jrnieder@gmail.com>
To: Elijah Newren <newren@gmail.com>
Cc: "Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
	"Phillip Wood" <phillip.wood@dunelm.org.uk>,
	"Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>,
	"Git Mailing List" <git@vger.kernel.org>,
	"Denton Liu" <liu.denton@gmail.com>,
	"Junio C Hamano" <gitster@pobox.com>,
	"Pavel Roskin" <plroskin@gmail.com>,
	"Alban Gruin" <alban.gruin@gmail.com>,
	"SZEDER Gábor" <szeder.dev@gmail.com>
Subject: Re: [PATCH v3 15/15] rebase: change the default backend from "am" to "merge"
Date: Thu, 16 Jan 2020 20:35:22 +0000
Message-ID: <20200116203521.GA71299@google.com> (raw)
In-Reply-To: <CABPp-BHODjbN3-snoFt4LDHGnoxhpDCQHhGVZp14gP1RZFp=hQ@mail.gmail.com>

Elijah Newren wrote:

> Thought about this ctags case a bit more.  In contrast to the
> deployment cases you brought up (which appear to be protected by a
> branch check anyway),

To be clear, one of the two deployment cases I mentioned (gh-pages) is
protected by a branch check, but the other (git --work-tree=srvroot
checkout) is not.

>                       doesn't this one argue more that post-commit
> should be run for all rebase types?  Sure, it'd take more computation
> time, but if a user runs "git pull --rebase" and then is frustrated
> that all their tags are extremely out of date then they may be kind of
> frustrated.

Yes.  In fact I think all of these examples argue for having the
post-commit hook run once on rebase completion (and on "git am"
completion, "git merge --ff-only" completion, etc).

Of course it's not hard to find other examples that argue against
that.  We provided a hook "here's a notification that runs after git
commit runs" without tailoring it to a particular need, and on one
hand people came up with various creative ways to use it (yay!) but on
the other hand it's hard to maintain as Git's ways of making new
commits evolve.

> Of course, arguing against myself, we could always tell them to just
> implement a post-rewrite hook.

That's an interesting facet I hadn't thought about before.

It's tempting since it kind of minimizes the blast surface while
providing people a way to keep doing what they had wanted.

Historically "git cherry-pick" ran "git commit", causing it to run the
post-commit hook.  There's some related discussion at
https://lore.kernel.org/git/20f33df8-7ba8-af26-e0c8-16152345c85b@talktalk.net/
of other side effects of having run "git commit".

... oh! git cherry-pick doesn't run post-rewrite.  Interesting.

To summarize what we've discussed so far:

 A. run post-commit hook consistently in rebase --am and --merge modes

    Advantages:
    * consistent with historic "rebase -i" behavior
    * supports hooks like ctags generation that want to update state to
      match what has been committed in the worktree (especially when
      preparing for the rebase to stop due to conflicts)
    * consistent with other commands like "git cherry-pick" that run the
      post-commit hook

    Disadvantages:
    * invokes hooks more often in a setting they are not used to being
      invoked in
    * slows down rebase
    * when post-commit hooks are used for deployment, exposes
      intermediate states in the middle of a rebase to the deployment
      environment
    * inconsistent with "git am"

    Mitigations:
    * could go through the normal warn about change, opt-in config,
      opt-out config cycle to make the change smoother
    * could provide new hooks (e.g., one run after a batch of objects
      is created for applications similar to "git gc --auto", one run
      when HEAD is updated for applications like the ctags one, one
      run on ref update for applications like the deployment case) and
      encourage authors to migrate to them
    * could run the post-commit hook in "git am", too

 B. stop running the post-commit hook in rebase

    Advantages:
    * makes --am and --merge consistent with minimal user impact

    Disadvantages:
    * meaning of the post-commit hook remains a muddle
    * in particular, "git am" and "git rebase" would not be consistent
      with "git cherry-pick"

    Mitigations:
    * could provide new hooks for people to migrate to to replace that
      muddle

 C. stop running the post-commit hook in rebase --merge or commit --amend

    Advantages:
    * produces a consistent definition of post-commit ("it's about new
      commits only")
    * hook authors get the same expressiveness using the post-rewrite hook

    Disadvantages:
    * the change to historical "git commit --amend" behavior is likely
      to be surprising

    Mitigations:
    * could go through the warn, opt-in config, opt-out config cycle

Any bits I've missed?

Thanks,
Jonathan

  reply index

Thread overview: 161+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-20 17:09 [PATCH 00/15] rebase: make the default backend configurable Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 01/15] rebase: extend the options for handling of empty commits Elijah Newren via GitGitGadget
2019-12-20 21:29   ` Junio C Hamano
2019-12-21  0:32     ` Elijah Newren
2019-12-21 18:52       ` Elijah Newren
2019-12-21 23:49       ` Junio C Hamano
2019-12-20 17:09 ` [PATCH 02/15] t3406: simplify an already simple test Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 03/15] rebase, sequencer: remove the broken GIT_QUIET handling Elijah Newren via GitGitGadget
2019-12-20 21:34   ` Junio C Hamano
2019-12-20 17:09 ` [PATCH 04/15] rebase: make sure to pass along the quiet flag to the sequencer Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 05/15] rebase: fix handling of restrict_revision Elijah Newren via GitGitGadget
2019-12-20 21:37   ` Junio C Hamano
2019-12-20 17:09 ` [PATCH 06/15] t3432: make these tests work with either am or merge backends Elijah Newren via GitGitGadget
2019-12-22  5:11   ` Denton Liu
2019-12-23 17:17     ` Elijah Newren
2019-12-20 17:09 ` [PATCH 07/15] rebase: allow more types of rebases to fast-forward Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 08/15] git-rebase.txt: add more details about behavioral differences of backends Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 09/15] rebase: move incompatibility checks between backend options a bit earlier Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 10/15] rebase: add an --am option Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 11/15] contrib: change the prompt for am-based rebases Elijah Newren via GitGitGadget
2019-12-20 23:07   ` SZEDER Gábor
2019-12-21  0:17     ` Elijah Newren
2019-12-20 17:09 ` [PATCH 12/15] rebase tests: mark tests specific to the am-backend with --am Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 13/15] rebase tests: repeat some tests using the merge backend instead of am Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 14/15] rebase: make the backend configurable via config setting Elijah Newren via GitGitGadget
2019-12-20 17:09 ` [PATCH 15/15] rebase: change the default backend from "am" to "merge" Elijah Newren via GitGitGadget
2019-12-20 18:51 ` [PATCH 00/15] rebase: make the default backend configurable Alban Gruin
2019-12-20 18:55   ` Elijah Newren
2019-12-23 18:49 ` [PATCH v2 " Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 01/15] rebase: extend the options for handling of empty commits Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 02/15] t3406: simplify an already simple test Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 03/15] rebase, sequencer: remove the broken GIT_QUIET handling Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 04/15] rebase: make sure to pass along the quiet flag to the sequencer Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 05/15] rebase: fix handling of restrict_revision Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 06/15] t3432: make these tests work with either am or merge backends Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 07/15] rebase: allow more types of rebases to fast-forward Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 08/15] git-rebase.txt: add more details about behavioral differences of backends Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 09/15] rebase: move incompatibility checks between backend options a bit earlier Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 10/15] rebase: add an --am option Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 11/15] contrib: change the prompt for interactive-based rebases Elijah Newren via GitGitGadget
2019-12-23 22:00     ` Denton Liu
2019-12-23 18:49   ` [PATCH v2 12/15] rebase tests: mark tests specific to the am-backend with --am Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 13/15] rebase tests: repeat some tests using the merge backend instead of am Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 14/15] rebase: make the backend configurable via config setting Elijah Newren via GitGitGadget
2019-12-23 18:49   ` [PATCH v2 15/15] rebase: change the default backend from "am" to "merge" Elijah Newren via GitGitGadget
2019-12-24 19:54   ` [PATCH v3 00/15] rebase: make the default backend configurable Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 01/15] rebase: extend the options for handling of empty commits Elijah Newren via GitGitGadget
2020-01-07 14:37       ` Phillip Wood
2020-01-07 19:15         ` Elijah Newren
2020-01-08 14:27           ` Phillip Wood
2020-01-09 21:32             ` Johannes Schindelin
2019-12-24 19:54     ` [PATCH v3 02/15] t3406: simplify an already simple test Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 03/15] rebase, sequencer: remove the broken GIT_QUIET handling Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 04/15] rebase: make sure to pass along the quiet flag to the sequencer Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 05/15] rebase: fix handling of restrict_revision Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 06/15] t3432: make these tests work with either am or merge backends Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 07/15] rebase: allow more types of rebases to fast-forward Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 08/15] git-rebase.txt: add more details about behavioral differences of backends Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 09/15] rebase: move incompatibility checks between backend options a bit earlier Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 10/15] rebase: add an --am option Elijah Newren via GitGitGadget
2020-01-07 14:43       ` Phillip Wood
2020-01-07 19:26         ` Elijah Newren
2020-01-07 20:11           ` Junio C Hamano
2020-01-08 14:32             ` Phillip Wood
2020-01-08 17:18               ` Junio C Hamano
2020-01-08 18:55                 ` Phillip Wood
2019-12-24 19:54     ` [PATCH v3 11/15] git-prompt: change the prompt for interactive-based rebases Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 12/15] rebase tests: mark tests specific to the am-backend with --am Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 13/15] rebase tests: repeat some tests using the merge backend instead of am Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 14/15] rebase: make the backend configurable via config setting Elijah Newren via GitGitGadget
2019-12-24 19:54     ` [PATCH v3 15/15] rebase: change the default backend from "am" to "merge" Elijah Newren via GitGitGadget
2020-01-10 23:14       ` Jonathan Nieder
2020-01-11  1:16         ` Elijah Newren
2020-01-11 14:41           ` Phillip Wood
2020-01-12 17:59             ` Johannes Schindelin
2020-01-16  6:32               ` Elijah Newren
2020-01-16  7:58                 ` Jonathan Nieder
2020-01-16  8:06                   ` Jonathan Nieder
2020-01-16 16:18                     ` Elijah Newren
2020-01-16 20:35                       ` Jonathan Nieder [this message]
2020-01-16 21:30                         ` Elijah Newren
2020-01-16 22:39                           ` Jonathan Nieder
2020-01-16 23:19                             ` Elijah Newren
2020-01-16 23:25                           ` Junio C Hamano
2020-01-17  0:51                             ` Elijah Newren
2020-01-16 15:35                   ` Elijah Newren
2020-01-16 20:05                   ` Junio C Hamano
2020-01-16 10:48                 ` Johannes Schindelin
2020-01-12 21:23             ` Junio C Hamano
2020-01-15 19:50             ` Jonathan Nieder
2020-01-15 21:59               ` Emily Shaffer
2020-01-16  6:14     ` [PATCH v4 00/19] rebase: make the default backend configurable Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 01/19] git-rebase.txt: update description of --allow-empty-message Elijah Newren via GitGitGadget
2020-02-09 15:59         ` Phillip Wood
2020-02-13 18:35           ` Elijah Newren
2020-01-16  6:14       ` [PATCH v4 02/19] t3404: directly test the behavior of interest Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 03/19] rebase (interactive-backend): make --keep-empty the default Elijah Newren via GitGitGadget
2020-02-09 15:59         ` Phillip Wood
2020-02-13 18:52           ` Elijah Newren
2020-01-16  6:14       ` [PATCH v4 04/19] rebase (interactive-backend): fix handling of commits that become empty Elijah Newren via GitGitGadget
2020-02-10 14:27         ` Phillip Wood
2020-02-13 18:54           ` Elijah Newren
2020-02-16 14:46             ` Phillip Wood
2020-01-16  6:14       ` [PATCH v4 05/19] t3406: simplify an already simple test Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 06/19] rebase, sequencer: remove the broken GIT_QUIET handling Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 07/19] rebase: make sure to pass along the quiet flag to the sequencer Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 08/19] rebase: fix handling of restrict_revision Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 09/19] t3432: make these tests work with either am or merge backends Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 10/19] rebase: allow more types of rebases to fast-forward Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 11/19] git-rebase.txt: add more details about behavioral differences of backends Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 12/19] rebase: move incompatibility checks between backend options a bit earlier Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 13/19] rebase: add an --am option Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 14/19] git-prompt: change the prompt for interactive-based rebases Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 15/19] rebase: drop '-i' from the reflog " Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 16/19] rebase tests: mark tests specific to the am-backend with --am Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 17/19] rebase tests: repeat some tests using the merge backend instead of am Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 18/19] rebase: make the backend configurable via config setting Elijah Newren via GitGitGadget
2020-01-16  6:14       ` [PATCH v4 19/19] rebase: change the default backend from "am" to "merge" Elijah Newren via GitGitGadget
2020-01-17 16:58       ` [PATCH v4 00/19] rebase: make the default backend configurable Phillip Wood
2020-02-05 21:06         ` Junio C Hamano
2020-02-05 22:38           ` Elijah Newren
2020-02-15 21:36       ` [PATCH v5 00/20] rebase: make the default backend configurable and change the default Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 01/20] git-rebase.txt: update description of --allow-empty-message Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 02/20] t3404: directly test the behavior of interest Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 03/20] rebase (interactive-backend): make --keep-empty the default Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 04/20] rebase (interactive-backend): fix handling of commits that become empty Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 05/20] t3406: simplify an already simple test Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 06/20] rebase, sequencer: remove the broken GIT_QUIET handling Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 07/20] rebase: make sure to pass along the quiet flag to the sequencer Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 08/20] rebase: fix handling of restrict_revision Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 09/20] t3432: make these tests work with either am or merge backends Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 10/20] rebase: allow more types of rebases to fast-forward Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 11/20] git-rebase.txt: add more details about behavioral differences of backends Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 12/20] rebase: move incompatibility checks between backend options a bit earlier Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 13/20] rebase: add an --am option Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 14/20] git-prompt: change the prompt for interactive-based rebases Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 15/20] rebase: drop '-i' from the reflog " Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 16/20] rebase tests: mark tests specific to the am-backend with --am Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 17/20] rebase tests: repeat some tests using the merge backend instead of am Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 18/20] rebase: make the backend configurable via config setting Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 19/20] rebase: change the default backend from "am" to "merge" Elijah Newren via GitGitGadget
2020-02-15 21:36         ` [PATCH v5 20/20] rebase: rename the two primary rebase backends Elijah Newren via GitGitGadget
2020-03-12 15:13           ` Emily Shaffer
2020-03-12 16:33             ` Elijah Newren
2020-03-12 17:55               ` Jonathan Nieder
2020-03-12 18:39                 ` Elijah Newren
2020-03-12 18:46                   ` Jonathan Nieder
2020-03-12 19:31                     ` Elijah Newren
2020-03-17  2:58                       ` Jonathan Nieder
2020-03-17  4:45                         ` Elijah Newren
2020-03-12 19:54                     ` Junio C Hamano
2020-03-12 19:07               ` Junio C Hamano
2020-03-12 19:12                 ` Jonathan Nieder
2020-03-12 19:12               ` Junio C Hamano
2020-03-12 19:29                 ` Elijah Newren
2020-03-12 20:37                   ` Jeff King
2020-03-12 21:27                     ` Junio C Hamano
2020-03-12 22:06                       ` Elijah Newren
2020-03-13  0:04                         ` Junio C Hamano
2020-03-12 23:30                       ` Jonathan Nieder
2020-02-16 15:01         ` [PATCH v5 00/20] rebase: make the default backend configurable and change the default Phillip Wood

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