From: Elijah Newren <newren@gmail.com>
To: "Eckhard Maaß" <eckhard.s.maass@googlemail.com>
Cc: Junio C Hamano <gitster@pobox.com>,
Ben Peart <peartben@gmail.com>,
Ben Peart <Ben.Peart@microsoft.com>,
"git@vger.kernel.org" <git@vger.kernel.org>,
"peff@peff.net" <peff@peff.net>,
"pclouds@gmail.com" <pclouds@gmail.com>,
"vmiklos@frugalware.org" <vmiklos@frugalware.org>,
Kevin Willford <kewillf@microsoft.com>,
"Johannes.Schindelin@gmx.de" <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH v3 2/3] merge: Add merge.renames config setting
Date: Fri, 27 Apr 2018 13:23:20 -0700 [thread overview]
Message-ID: <CABPp-BHwM1jx2+VTxt7hga7v-E6gvHuxVNPqm-MPRXYe5CDVtA@mail.gmail.com> (raw)
In-Reply-To: <20180427183752.GA2799@esm>
On Fri, Apr 27, 2018 at 11:37 AM, Eckhard Maaß
<eckhard.s.maass@googlemail.com> wrote:
> On Fri, Apr 27, 2018 at 11:23:56AM +0900, Junio C Hamano wrote:
>> I think demoting from copy to rename-only is a good idea, at least
>> for now, because I do not believe we have figured out what we want
>> to happen when we detect copied files are involved in a merge.
>
> Does anyone know some threads concerning that topic? I tried to search
> for it, but somehow "merge copy detection" did not find me useful
> threads so far. I would be interested in that topic anyway, so I would
> like to know what the ideas are that floated so far.
>
I doubt it has ever been discussed before this thread. But, if you're
curious, I'll try to dump a few thoughts. Let's say we have branches
A and B, and:
A: modifies file z
B: copies z to y
Should the modifications to z done in A propagate to both z and y? If
not, what good is copy detection? If so, then there are several
ramifications...
- If B not only copied z but also first modified it, then do we have
potential conflicts with both z and y -- possibly the exact same
conflicts, making the user resolve them repeatedly?
- What if A copied z to x? Do changes to z propagate to all three of
z and x and y? Do changes to either x or y affect z? Do they
affect each other?
- If A deleted z, does that give us a copy/delete conflict for y? Do
we also have to worry about copy/add conflicts? copy/add/delete?
rename/copy (multiple variants)? copy/copy?
- Extra degrees of freedom may mean new conflict types:
- The extra degrees of freedom from renames introduced multiple new
conflict types (e.g. rename/add, rename/rename(1to2),
rename/rename(2to1)).
- Directory rename detection added more (rename/rename/rename(1to3),
rename/rename(Nto1), add/add/add, directory/file/file, n-fold
transitive rename, etc.), -- and forced us to specify various
rules to limit the possibility space so that conflicts could be
representable in the index and understandable by the user.
- I suspect adding copies would add new types of conflicts we
haven't thought of yet.
The more I think about it, the more I think that attempting to detect
copies in a merge algorithm just doesn't make sense. Anything I can
think of that someone might attempt to use detected copies for would
just surprise users in a bad way...and it'd open up a big can of edge
and corner case problems as well.
next prev parent reply other threads:[~2018-04-27 20:23 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-20 13:36 [PATCH v1 0/2] add additional config settings for merge Ben Peart
2018-04-20 13:36 ` [PATCH v1 1/2] merge: Add merge.renames config setting Ben Peart
2018-04-20 17:02 ` Elijah Newren
2018-04-20 17:26 ` Elijah Newren
2018-04-23 12:57 ` Ben Peart
2018-04-20 17:59 ` Ben Peart
2018-04-20 18:34 ` Elijah Newren
2018-04-21 4:23 ` Junio C Hamano
2018-04-23 16:00 ` Ben Peart
2018-04-23 23:23 ` Junio C Hamano
2018-04-24 11:58 ` Johannes Schindelin
2018-04-24 17:47 ` Elijah Newren
2018-04-25 8:20 ` Johannes Schindelin
2018-04-22 12:07 ` Eckhard Maaß
2018-04-23 13:15 ` Ben Peart
2018-04-23 21:32 ` Eckhard Maaß
2018-04-24 16:53 ` Ben Peart
2018-04-23 13:22 ` Ben Peart
2018-04-20 13:36 ` [PATCH v1 2/2] merge: Add merge.aggressive " Ben Peart
2018-04-20 17:22 ` Elijah Newren
2018-04-24 16:45 ` Ben Peart
2018-04-24 17:36 ` Elijah Newren
2018-04-24 23:57 ` Junio C Hamano
2018-04-25 14:47 ` Ben Peart
2018-04-20 17:34 ` [PATCH v1 0/2] add additional config settings for merge Elijah Newren
2018-04-20 18:19 ` Ben Peart
2018-04-24 17:11 ` [PATCH v2 " Ben Peart
2018-04-24 17:11 ` [PATCH v2 1/2] merge: Add merge.renames config setting Ben Peart
2018-04-24 18:11 ` Elijah Newren
2018-04-24 18:59 ` Elijah Newren
2018-04-24 20:31 ` Ben Peart
2018-04-25 16:01 ` Elijah Newren
2018-04-24 17:11 ` [PATCH v2 2/2] merge: Add merge.aggressive " Ben Peart
2018-04-25 0:13 ` [PATCH v2 0/2] add additional config settings for merge Junio C Hamano
2018-04-25 15:22 ` Ben Peart
2018-04-26 1:48 ` Junio C Hamano
2018-04-26 20:52 ` [PATCH v3 0/3] add merge.renames config setting Ben Peart
2018-04-26 20:52 ` [PATCH v3 1/3] merge: update documentation for {merge,diff}.renameLimit Ben Peart
2018-04-26 23:11 ` Elijah Newren
2018-04-26 23:23 ` Jonathan Tan
2018-04-26 20:52 ` [PATCH v3 2/3] merge: Add merge.renames config setting Ben Peart
2018-04-26 22:52 ` Elijah Newren
2018-04-27 0:54 ` Ben Peart
2018-04-27 2:23 ` Junio C Hamano
2018-04-27 3:28 ` Elijah Newren
2018-04-27 7:23 ` Johannes Schindelin
2018-04-27 14:32 ` Elijah Newren
2018-04-27 18:37 ` Eckhard Maaß
2018-04-27 20:23 ` Elijah Newren [this message]
2018-04-30 8:03 ` Eckhard Maaß
2018-04-30 16:54 ` Elijah Newren
2018-04-27 4:17 ` Elijah Newren
2018-04-27 18:19 ` Elijah Newren
2018-04-30 13:11 ` Ben Peart
2018-04-30 16:12 ` Re: Elijah Newren
2018-05-02 14:33 ` Re: Ben Peart
2018-04-26 20:52 ` [PATCH v3 3/3] merge: pass aggressive when rename detection is turned off Ben Peart
2018-04-26 23:00 ` Elijah Newren
2018-04-26 22:08 ` [PATCH v3 0/3] add merge.renames config setting Elijah Newren
2018-05-02 16:01 ` [PATCH v4 0/3] add additional config settings for merge Ben Peart
2018-05-02 16:01 ` [PATCH v4 1/3] merge: update documentation for {merge,diff}.renameLimit Ben Peart
2018-05-02 16:01 ` [PATCH v4 2/3] merge: Add merge.renames config setting Ben Peart
2018-05-04 3:07 ` Junio C Hamano
2018-05-02 16:01 ` [PATCH v4 3/3] merge: pass aggressive when rename detection is turned off Ben Peart
2018-05-02 17:20 ` [PATCH v4 0/3] add additional config settings for merge Elijah Newren
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