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From: Phillip Wood <phillip.wood@talktalk.net>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>,
	Igor Djordjevic <igor.d.djordjevic@gmail.com>
Cc: Phillip Wood <phillip.wood@dunelm.org.uk>,
	Jacob Keller <jacob.keller@gmail.com>,
	Sergey Organov <sorganov@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: Thu, 8 Mar 2018 12:16:41 +0000
Message-ID: <483674f8-4097-a374-c8f3-cf56cbb92042@talktalk.net> (raw)
In-Reply-To: <c5a5c2cc-6a11-440f-5b9b-964ae1ca07dd@talktalk.net>

On 08/03/18 11:20, Phillip Wood wrote:
> On 07/03/18 07:26, Johannes Schindelin wrote:
>> Hi Buga,
>>
>> On Tue, 6 Mar 2018, Igor Djordjevic wrote:
>>
>>> On 06/03/2018 19:12, Johannes Schindelin wrote:
>>>>
>>>>>> And I guess being consistent is pretty important, too - if you add new
>>>>>> content during merge rebase, it should always show up in the merge,
>>>>>> period. 
>>>>>
>>>>> Yes, that should make it easy for the user to know what to expect from
>>>>> rebase.
>>>>
>>>> [...]
>>>>
>>>> It will be slightly inconsistent. But in a defendable way, I think.
>>>
>>> I like where this discussion is heading, and here`s what I thought 
>>> about it :)
>>>
>>> [...]
>>>
>>> Here`s a twist - not letting `merge` trying to be too smart by 
>>> figuring out whether passed arguments correspond to rewritten 
>>> versions of the original merge parents (which would be too 
>>> restrictive, too, I`m afraid), but just be explicit about it, instead!
>>
>> That's the missing piece, I think.
>>
>>> So, it could be something like:
>>>
>>> 	merge -C deadbee 123abc:cafecafe 234bcd:bedbedbed
>>
>> I like where this is heading, too, but I do not think that we can do this
>> on a per-MERGE_HEAD basis. The vast majority of merge commits, in
>> practice, have two parents. So the `merge` command would actually only
>> have one revision to merge (because HEAD is the implicit first parent). So
>> that is easy.
>>
>> But as soon as you go octopus, you can either perform an octopus merge, or
>> rebase the original merge commit. You cannot really mix and match here.
>>
>> Unless we reimplement the octopus merge (which works quite a bit
>> differently from the "rebase merge commit" strategy, even if it is
>> incremental, too), which has its own challenges: if there are merge
>> conflicts before merging the last MERGE_HEAD, the octopus merge will exit
>> with status 2, telling you "Should not be doing an octopus.". While we
>> will want to keep merge conflict markers and continue with the "rebase the
>> original merge commit" strategy.
>>
>> And it would slam the door shut for adding support for *other* merge
>> strategies to perform a more-than-two-parents merge.
>>
>> Also, I do not think that it makes a whole lot of sense in practice to let
>> users edit what will be used for "original parent". If the user wants to
>> do complicated stuff, they can already do that, via `exec`. The `merge`
>> command really should be about facilitating common workflows, guiding the
>> user to what is sane.
>>
>> Currently my favorite idea is to introduce a new flag: -R (for "rebase the
>> original merge commit"). It would look like this:
>>
>> 	merge -R -C <original-merge> <merge-head> # <oneline>
>>
>> This flag would of course trigger the consistency check (does the number
>> of parents of the original merge commit agree with the parameter list? Was
>> an original merge commit specified to begin with?), and it would not fall
>> back to the recursive merge, but error out if that check failed.
>>
>> Side note: I wonder whether we really need to perform the additional check
>> that ensures that the <merge-head> refers to the rewritten version of the
>> original merge commit's parent.
>>
>> Second side note: if we can fast-forward, currently we prefer that, and I
>> think we should keep that behavior with -R, too.
> 
> I think that would be a good idea to avoid unpleasant surprises.

Oops that was referring to the first side note. I think fast forwarding
is a good idea. I'm not so sure about checking that <merge-head> refers
to the rewritten version of the original merge commit's parent any more
though. Having thought some more, I think we would want to allow the
user to rearrange a topic branch that is the parent of a merge and that
would require allowing a different parent as the old parent could be
dropped or swapped with another commit in the branch. I can't think of a
way to mechanically check that the new parent is 'somehow derived from'
the old one.

>> If the user wants to force a new merge, they simply remove that -R flag.
>>
>> What do you think?
> 
> I did wonder about using 'pick <original-merge>' for rebasing merges and
> keeping 'merge ...' for recreating them but I'm not sure if that is a
> good idea. It has the advantage that the user cannot specify the wrong
> parents for the merge to be rebased as 'git rebase' would work out if
> the parents have been rebased, but maybe it's a bit magical to use pick
> for merge commits. Also there isn't such a simple way for the user to go
> from 'rabase this merge' to 'recreate this merge' as they'd have to
> write the whole merge line themselves (though I guess something like
> emacs' git-rebase.el would be able to help with that)

Scrub that, it is too magical and I don't think it would work with
rearranged commits - it's making the --preserve-merges mistake all over
again. It's a shame to have 'merge' mean 'recreate the merge' and
'rebase the merge' but I don't think there is an easy way round that.

> Best Wishes
> 
> Phillip
> 
> 
>> Ciao,
>> Dscho
>>
> 


  reply index

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 [this message]
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
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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