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From: Phillip Wood <phillip.wood123@gmail.com>
To: Alex Henrie <alexhenrie24@gmail.com>
Cc: git@vger.kernel.org, tao@klerks.biz, gitster@pobox.com,
	newren@gmail.com, phillip.wood123@gmail.com,
	Johannes.Schindelin@gmx.de, sorganov@gmail.com,
	Glen Choo <chooglen@google.com>,
	Calvin Wan <calvinwan@google.com>
Subject: Re: [PATCH v5 3/3] rebase: add a config option for --rebase-merges
Date: Mon, 13 Mar 2023 14:20:46 +0000	[thread overview]
Message-ID: <f8dc5bd3-b325-1e11-6e2d-6d202271f9ff@dunelm.org.uk> (raw)
In-Reply-To: <CAMMLpeTUbG+b89acan-GXGS4H=J7aQupbK8zdxwNg__U_We2dw@mail.gmail.com>

Hi Alex

On 12/03/2023 20:57, Alex Henrie wrote:
> On Tue, Mar 7, 2023 at 9:23 AM Phillip Wood <phillip.wood123@gmail.com> wrote:
> 
>> On 04/03/2023 23:24, Alex Henrie wrote:
>>> On Thu, Mar 2, 2023 at 2:37 AM Phillip Wood <phillip.wood123@gmail.com> wrote:
>>>
>>>> On 25/02/2023 18:03, Alex Henrie wrote:
>>>
>>>>> +rebase.merges::
>>>>> +     Whether and how to set the `--rebase-merges` option by default. Can
>>>>> +     be `rebase-cousins`, `no-rebase-cousins`, or a boolean. Setting to
>>>>> +     true is equivalent to `--rebase-merges` without an argument, setting to
>>>>> +     `rebase-cousins` or `no-rebase-cousins` is equivalent to
>>>>> +     `--rebase-merges` with that value as its argument, and setting to false
>>>>> +     is equivalent to `--no-rebase-merges`. Passing `--rebase-merges` on the
>>>>> +     command line without an argument overrides a `rebase.merges=false`
>>>>> +     configuration but does not override other values of `rebase.merge`.
>>>>
>>>> I'm still not clear why the commandline doesn't override the config in
>>>> all cases as is our usual practice. After all if the user has set
>>>> rebase.merges then they don't need to pass --rebase-merges unless they
>>>> want to override the config.
>>>
>>> Given the current push to turn rebase-merges on by default, it seems
>>> likely that rebase-cousins will also be turned on by default at some
>>> point after that.
>>
>> It is good to try and future proof things but this seems rather
>> hypothetical. I don't really see how the choice of whether
>> --rebase-merges is turned on by default is related to the choice of
>> whether or not to rebase cousins by default. It is worth noting that the
>> default was changed to from rebase-cousins to no-rebase-cousins early in
>> the development of --rebase-merges[1] as it was felt to be less surprising.
> 
>> [1]
>> https://lore.kernel.org/git/nycvar.QRO.7.76.6.1801292251240.35@ZVAVAG-6OXH6DA.rhebcr.pbec.zvpebfbsg.pbz/
> 
> Thank you for sharing that link. Even though I got the tests right, I
> got confused and started thinking that rebase-cousins was a more
> thorough version of rebase-merges. In fact, they do opposite things:
> rebase-merges tries to preserve the graph and rebase-cousins
> intentionally restructures the graph. In my opinion using the word
> "rebase" in the names of both options was another unfortunate UI
> decision, but I understand the difference now.
> 
>>> There will be a warning about the default changing,
>>> and we'll want to let users suppress that warning by setting
>>> rebase.rebaseMerges=rebase-cousins. It would then be very confusing if
>>> a --rebase-merges from some old alias continued to mean
>>> --rebase-merges=no-rebase-cousins when the user expects it to start
>>> behaving as though the default has already changed.
>>
>> But aren't you breaking those aliases now when
>> rebase.rebaseMerges=rebase-cousins? That's what I'm objecting to. It
>> seems like we're breaking things now to avoid a hypothetical future
>> change breaking them which does not seem like the right trade off to me.
>>
>> It also does not fit with the way other optional arguments interact with
>> their associated config setting. For example "git branch/checkout/switch
>> --track" and branch.autoSetupMerge. If the optional argument to --track
>> is omitted it defaults to "direct" irrespective of the config.
 >
> What I really don't want is to paint ourselves into a corner.

Nor do I but we already seem to be in some kind of corner as what you're 
proposing breaks the status quo and the existing convention that command 
line options override config settings.

> You're
> right that it's unlikely that the default will ever change from
> no-rebase-cousins to rebase-cousins; I was mistaken. However, Glen
> thinks that in the future we might have some kind of
> rebase-evil-merges mode as well, and that that might become the
> default. If we don't let the rebase.rebaseMerges config value control
> the default behavior of --rebase-merges without an argument on the
> command line, we would have to introduce a separate config option for
> the transition, which would be ugly.

I'm optimistic that Elijah's work on rebasing evil merges will allow us 
to improve --rebase-merges. I expect that we'll enable it by default 
once it is merged. I do not think that we should add another argument 
for --rebase-merges to disable it though as that would be orthogonal to 
"rebase-cousins" and "no-rebase-cousins" which control what commits get 
rebased not how merges are rebased. If users want to disable the better 
rebasing of merges we'll need to add a --remerge option or something 
like that.

> More voices would be helpful here. Does anyone else have an opinion on
> how likely it is that the default rebase-merges mode will change in
> the future? Or on whether rebase.rebaseMerges should be allowed to
> affect --rebase-merges in order to facilitate such a change?

Getting other's views would indeed be helpful

Best Wishes

Phillip


>>>>> +test_expect_success '--rebase-merges overrides rebase.merges=false' '
>>>>> +     test_config rebase.merges false &&
>>>>> +     git checkout -b override-config-merges-false E &&
>>>>> +     before="$(git rev-parse --verify HEAD)" &&
>>>>> +     test_tick &&
>>>>> +     git rebase --rebase-merges C &&
>>>>> +     test_cmp_rev HEAD $before
>>>>
>>>> This test passes if the rebase does nothing, maybe pass --force and
>>>> check the graph?
>>>
>>> The rebase is supposed to do nothing here.
>>
>> It's not doing nothing though - it is rebasing the branch, it just
>> happens that everything fast-forwards so HEAD ends up unchanged. My
>> point is that this test should verify the branch has been rebased. Maybe
>> you could check the reflog message for HEAD@{0} is
>>
>>          rebase (finish): returning to refs/heads/override-config-merges-false
>>
>>> Checking that the commit
>>> hash is the same is just a quick way to check that the entire graph is
>>> the same. What more would be checked by checking the graph instead of
>>> the hash?
>>
>> By using --force and checking the graph you check that the rebase
>> actually happened.
> 
> I got the impression that people like that not checking the graph
> itself (or the reflog) makes the tests more concise, but I don't care
> much either way. For what it's worth, the way I did it matches the
> existing tests in the file. If you can find at least one other person
> who thinks that it ought to change for this patch series to be
> accepted, and no one else objects, I'll change it.
> 
>> Thanks for working on this
> 
> You're welcome; hopefully we can get the remaining details ironed out quickly.
> 
> -Alex

  reply	other threads:[~2023-03-13 14:20 UTC|newest]

Thread overview: 96+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-23  5:34 [PATCH v4 1/3] rebase: add documentation and test for --no-rebase-merges Alex Henrie
2023-02-23  5:34 ` [PATCH v4 2/3] rebase: stop accepting --rebase-merges="" Alex Henrie
2023-02-24 13:54   ` Johannes Schindelin
2023-02-24 17:20     ` Junio C Hamano
2023-02-24 17:50       ` Alex Henrie
2023-02-24 18:08         ` Junio C Hamano
2023-02-24 18:23           ` Alex Henrie
2023-02-24 18:40             ` Junio C Hamano
2023-02-24 18:55               ` Alex Henrie
2023-02-24 19:13                 ` Junio C Hamano
2023-02-24 19:24                   ` Alex Henrie
2023-02-24 19:24                   ` Phillip Wood
2023-02-24 19:56                     ` Alex Henrie
2023-02-23  5:34 ` [PATCH v4 3/3] rebase: add a config option for --rebase-merges Alex Henrie
2023-02-24 13:53   ` Johannes Schindelin
2023-02-24 17:49     ` Alex Henrie
2023-02-24 14:55   ` Phillip Wood
2023-02-24 17:51     ` Alex Henrie
2023-02-23 17:28 ` [PATCH v4 1/3] rebase: add documentation and test for --no-rebase-merges Junio C Hamano
2023-02-24 13:57   ` Johannes Schindelin
2023-02-24 19:16     ` Junio C Hamano
2023-02-25 18:09     ` Alex Henrie
2023-02-25 18:03 ` [PATCH v5 0/3] rebase: add a config option for --rebase-merges Alex Henrie
2023-02-25 18:03   ` [PATCH v5 1/3] rebase: add documentation and test for --no-rebase-merges Alex Henrie
2023-03-01 23:23     ` Glen Choo
2023-02-25 18:03   ` [PATCH v5 2/3] rebase: deprecate --rebase-merges="" Alex Henrie
2023-03-01 23:46     ` Glen Choo
2023-03-02 10:07     ` Phillip Wood
2023-03-02 18:02     ` Calvin Wan
2023-02-25 18:03   ` [PATCH v5 3/3] rebase: add a config option for --rebase-merges Alex Henrie
2023-03-01 23:43     ` Glen Choo
2023-03-02  9:37     ` Phillip Wood
2023-03-04 23:24       ` Alex Henrie
2023-03-07 16:23         ` Phillip Wood
2023-03-12 20:57           ` Alex Henrie
2023-03-13 14:20             ` Phillip Wood [this message]
2023-03-13 16:12               ` Felipe Contreras
2023-03-13 19:46             ` Junio C Hamano
2023-03-24 14:47             ` About replaying "evil" merges... " Johannes Schindelin
2023-03-02 18:02     ` Calvin Wan
2023-03-04 23:24       ` Alex Henrie
2023-03-01 23:14   ` [PATCH v5 0/3] " Glen Choo
2023-03-02  5:02     ` Alex Henrie
2023-03-02  5:09       ` Alex Henrie
2023-03-05  5:07   ` [PATCH v6 0/3] rebase: document, clean up, and introduce " Alex Henrie
2023-03-05  5:07     ` [PATCH v6 1/3] rebase: add documentation and test for --no-rebase-merges Alex Henrie
2023-03-08 22:25       ` Sergey Organov
2023-03-05  5:07     ` [PATCH v6 2/3] rebase: deprecate --rebase-merges="" Alex Henrie
2023-03-07 14:59       ` Phillip Wood
2023-03-05  5:07     ` [PATCH v6 3/3] rebase: add a config option for --rebase-merges Alex Henrie
2023-03-07 14:56       ` Phillip Wood
2023-03-07 18:32         ` Junio C Hamano
2023-03-12 21:01           ` Alex Henrie
2023-03-08  0:09         ` Glen Choo
2023-03-08  0:02       ` Glen Choo
2023-03-12 21:03         ` Alex Henrie
2023-03-15  2:52         ` Alex Henrie
2023-03-16 17:32           ` Glen Choo
2023-03-16 18:11             ` Felipe Contreras
2023-03-16 22:46               ` Glen Choo
2023-03-16 23:48                 ` Felipe Contreras
2023-03-16 20:27             ` Alex Henrie
2023-03-16 22:39               ` Glen Choo
2023-03-18  5:59                 ` Alex Henrie
2023-03-24 15:05               ` Johannes Schindelin
2023-03-25 16:59               ` Sergey Organov
2023-03-05 12:22     ` [PATCH v6 0/3] rebase: document, clean up, and introduce " Sergey Organov
2023-03-05 21:33       ` Alex Henrie
2023-03-05 22:54         ` Sergey Organov
2023-03-06  0:02           ` Alex Henrie
2023-03-06 13:23             ` Sergey Organov
2023-03-06 19:08             ` Junio C Hamano
2023-03-06 17:19           ` Junio C Hamano
2023-03-06 16:24     ` Phillip Wood
2023-03-06 17:36       ` Alex Henrie
2023-03-07 15:07         ` Phillip Wood
2023-03-08  0:13     ` Glen Choo
2023-03-12 21:04     ` [PATCH v7 " Alex Henrie
2023-03-12 21:04       ` [PATCH v7 1/3] rebase: add documentation and test for --no-rebase-merges Alex Henrie
2023-03-12 21:04       ` [PATCH v7 2/3] rebase: deprecate --rebase-merges="" Alex Henrie
2023-03-12 21:04       ` [PATCH v7 3/3] rebase: add a config option for --rebase-merges Alex Henrie
2023-03-20  5:59       ` [PATCH v8 0/3] rebase: document, clean up, and introduce " Alex Henrie
2023-03-20  5:59         ` [PATCH v8 1/3] rebase: add documentation and test for --no-rebase-merges Alex Henrie
2023-03-20  5:59         ` [PATCH v8 2/3] rebase: deprecate --rebase-merges="" Alex Henrie
2023-03-20  5:59         ` [PATCH v8 3/3] rebase: add a config option for --rebase-merges Alex Henrie
2023-03-22 16:54           ` Phillip Wood
2023-03-23 18:45             ` Junio C Hamano
2023-03-24 14:52               ` Phillip Wood
2023-03-25  5:23               ` Alex Henrie
2023-03-25  5:21             ` Alex Henrie
2023-03-26  3:06         ` [PATCH v9 0/3] rebase: document, clean up, and introduce " Alex Henrie
2023-03-26  3:06           ` [PATCH v9 1/3] rebase: add documentation and test for --no-rebase-merges Alex Henrie
2023-03-26  3:06           ` [PATCH v9 2/3] rebase: deprecate --rebase-merges="" Alex Henrie
2023-03-26  3:06           ` [PATCH v9 3/3] rebase: add a config option for --rebase-merges Alex Henrie
2023-03-26 15:12           ` [PATCH v9 0/3] rebase: document, clean up, and introduce " Phillip Wood
2023-03-27 16:33             ` Junio C Hamano

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