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From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Igor Djordjevic <igor.d.djordjevic@gmail.com>
Cc: 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: Mon, 26 Mar 2018 15:07:32 +0200 (DST)
Message-ID: <nycvar.QRO.7.76.6.1803261455130.77@ZVAVAG-6OXH6DA.rhebcr.pbec.zvpebfbsg.pbz> (raw)
In-Reply-To: <243ca23d-77a9-4ae1-a120-de6c6b195cdc@gmail.com>

Hi Buga,

On Tue, 13 Mar 2018, Igor Djordjevic wrote:

> On 12/03/2018 11:46, Johannes Schindelin wrote:
> > 
> > > Sometimes one just needs to read the manual, and I don`t really
> > > think this is a ton complicated, but just something we didn`t really
> > > have before (real merge rebasing), so it requires a moment to grasp
> > > the concept.
> > 
> > If that were the case, we would not keep getting bug reports about
> > --preserve-merges failing to reorder patches.
> 
> Not sure where that is heading to, but what I`m arguing about is that 
> introducing new commands and concepts (`merge`, and with `-R`) just 
> makes the situation even worse (more stuff to grasp).

The problem with re-using `pick` is that its concept does not apply to
merges. The cherry-pick of a non-merge commit is well-defined: the current
HEAD is implicitly chosen as the cherry-picked commit's (single) parent
commit. There is no ambiguity here.

But for merge commits, we need to specify the parent commits (apart from
the first one) *explicitly*. There was no need for that in the `pick`
command, nor in the concept of a cherry-pick.

> Reusing existing concepts where possible doesn`t have this problem.

Existing concepts are great. As long as they fit the requirements of the
new scenarios. In this case, `pick` does *not* fit the requirement of
"rebase a merge commit".

If you really want to force the `pick` concept onto the use case where you
need to "reapply" merges, then the closest you get really is Sergey's
idea, which I came to reject when considering its practical implications.

Even so, you would have to make the `pick` command more complicated to
support merge commits. And whatever you would do to extend the `pick`
command would *not make any sense* to the current use case of the `pick`
command.

The real problem, of course, is that a non-merge commit, when viewed from
the perspective of the changes it introduced, is a very different beast
than a merge commit: it does not need to reconcile changes, ever, because
there is really only one "patch" to one revision. That is very different
from a merge commit, whose changes can even disagree with one another (and
in fact be resolved with changes disagreeing *yet again*)!

> > > Saying in favor of `--rebase-merges`, you mean as a separate option,
> > > alongside `--recreate-merges` (once that series lands)?
> > 
> > No. I am against yet another option. The only reason I pollute the
> > option name space further with --recreate-merges is that it would be
> > confusing to users if the new mode was called --preserve-merges=v2
> > (but work *totally differently*).
> 
> I see. So I take you`re thinking about renaming `--recreate-merges` to
> `--rebase-merges` instead?

Thinking about it. Nothing will happen before v2.17.0 on that front,
though, because -- unlike you gentle people -- I have to focus on
stabilizing Git's code base now.

> That would seem sensible, too, I think, being the default usage mode in
> the first place. Being able to actually (re)create merges, too, once
> user goes interactive, would be "just" an additional (nice and powerful)
> feature on top of it.

The implementation detail is, of course, that I will introduce this with
the technically-simpler strategy: always recreating merge commits with the
recursive strategy. A follow-up patch series will add support for rebasing
merge commits, and then use it by default.

This latter part will need a lot of experimentation, though. That's why I
want the --recreate-merges patch series cooking in `next` first.

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
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 [this message]
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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