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From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Thomas Gummerer <t.gummerer@gmail.com>
Cc: Christian Couder <christian.couder@gmail.com>,
	git <git@vger.kernel.org>, Jeff King <peff@peff.net>,
	SZEDER Gábor <szeder.dev@gmail.com>,
	Оля Тележная  <olyatelezhnaya@gmail.com>,
	Matthieu Moy <Matthieu.Moy@gmail.com>
Subject: Re: GSoC 2019: Git's application submitted
Date: Thu, 7 Feb 2019 20:39:08 +0100 (STD)
Message-ID: <nycvar.QRO.7.76.6.1902072023250.41@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <20190206220942.GE6085@hank.intra.tgummerer.com>

Hi Thomas,

On Wed, 6 Feb 2019, Thomas Gummerer wrote:

> I think the idea here could definitely be split into a couple different
> phases, that could be individually useful, and can be merged
> individually, though I don't know if they would necessarily be.

Good idea.

> Of the top of my head:
> 
>  - write test_expect_failure tests for the expected new behaviour
> 
>    This may not be worth including in git.git yet, but it can be a
>    very useful starting point for somebody else continuing the feature
>    if the student finds they don't have time for it.

I like this approach.

>  - implement pushing the index state, without dealing with conflicts
>  - implement poping the index state, without dealing with conflicts
> 
>    This can already be individually useful, and I think this is
>    something people asked for on the mailing list, though I didn't try
>    digging up old threads for now.  After these two steps stashing and
>    restoring a merge conflict would still not work, but we have a good
>    first step that could be merged.

We already have `git stash --keep-index`. Is this what you mean here?

>  - implement pushing/poping conflicted state
> 
>    This would obviously be the end goal.

On second thought, this might actually be super trivial. Right now, we
support two modes (not counting the `--untracked` stuff): --keep-index and
--no-keep-index. In both cases, we seem to create a merge commit whose
tree reflects the working directory and whose first parent is HEAD and
whose second parent is a single commit on top of HEAD (which contains
either no changes in the case of --no-keep-index, or whose tree reflects
the index in case of --keep-index).

To extend that to the conflict case, we could introduce a new flag
--with-conflicts, and have the commit structure

	Worktree
	 |    \
	 |    index stage 0
	 |      /     |     \
	 | stage 1  stage 2  stage 3
	 |    /     /       /
	HEAD ---------------

The only tricky thing I can see is to maintain backwards compatibility if
possible, so that old `git stash` will do something at least semi-sensible
with those commit structures.

It might be too small a project, after all.

Ciao,
Dscho

> > Another potential issue is that a new feature might be prone to naming
> > or user interface discussions which could last for a long time or
> > could not result in clear decisions.
> 
> Yes, this is definitely a potential pitfall.  I haven't thought in
> depth about the interface yet, but I think the discussion around that
> would be something we as mentors could and should guide the student
> through.  We also wouldn't make the feature the default from the
> beginning, but introduce it behind a new flag/maybe a config option,
> to make sure we don't introduce any backwards compatible changes.
> 
> It's probably also something the student should include in their
> proposal, so we can get eyes on it early in the process.
> 
> > So I think we should be very careful if we propose a project that
> > implements a new feature to a student. We should at least consider the
> > above potential issues and see if they can be mitigated before the
> > project starts.
> 
> Thanks for bringing these issues up, they are definitely useful to
> work through.  
> 
> > Thank you anyway for proposing this idea,
> > Christian.
> 

  reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-04  9:16 Christian Couder
     [not found] ` <CAL21Bm=K6zZ=APkiP3A_X7xVoOfx-MY2435YMp5y1ztE-xyYtg@mail.gmail.com>
2019-02-04 12:54   ` Christian Couder
2019-02-04 21:52 ` Thomas Gummerer
2019-02-05 21:17   ` Thomas Gummerer
2019-02-05 22:00     ` Christian Couder
2019-02-06 22:09       ` Thomas Gummerer
2019-02-07 19:39         ` Johannes Schindelin [this message]
2019-02-07 21:33           ` Thomas Gummerer
2019-02-11  5:41             ` Оля Тележная
2019-02-11  7:45               ` Christian Couder
2019-02-11  8:31                 ` Оля Тележная
2019-02-11 10:52                   ` Christian Couder
2019-02-13 22:36               ` Elijah Newren
2019-02-14  9:48                 ` Christian Couder
2019-02-11  8:35             ` Christian Couder
2019-02-11 22:18               ` Thomas Gummerer
2019-02-11 23:58                 ` Christian Couder
2019-02-12 20:25                   ` Thomas Gummerer
2019-02-12 20:49                     ` Christian Couder
2019-02-12 22:13                       ` Thomas Gummerer
2019-02-06 12:27     ` Johannes Schindelin
2019-03-05 12:04 ` Duy Nguyen
2019-03-05 12:23   ` Duy Nguyen
2019-03-06  4:49   ` Jeff King
2019-03-06  9:36     ` Duy Nguyen
2019-03-06 19:08       ` Jeff King
2019-03-06 14:16     ` Johannes Schindelin
2019-03-18 12:51 ` Duy Nguyen
2019-03-18 16:37   ` Christian Couder

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