mergetools: add new conflict marker format with diffs in
I use 3-way conflict markers. Often when I resolve them, I manually
compare one the base with one side and apply the differences to the
other side. That can be hard when the conflict marker is large. This
patch introduces a new type of conflict marker, which I'm hoping will
make it easier to resolve conflicts.
The new format uses `<<<<<<<` and `>>>>>>>` to open and close the
markers, just like our existing 2-way and 3-way conflict
markers. Instead of having 2 or 3 snapshots (left+right or
left+base+right), it has a sequence of diffs. A diff looks like this:
```
------- base
+++++++ left
a
-b
+c
d
```
A diff that adds one side ("diff from nothing") has a `=======` header
instead and does not have have `+` prefixed on its lines. A regular
3-way merge can be viewed as adding one side plus a diff between the
base and the other side. It thus has two ways of being represented,
depending on which side is being diffed:
```
<<<<<<<
======= left
contents
on
left
------- base
+++++++ right
contents
on
-left
+right
>>>>>>>
```
or
```
<<<<<<<
------- base
+++++++ left
contents
on
-right
+left
======= right
contents
on
right
>>>>>>>
```
I've made it so the new merge tool tries to pick a version that has
the most common lines (no difference in the example above).
I've called the new tool "mergediff" to stick to the convention of
starting with "merge" if the tool tries a regular 3-way merge.
The idea came from my pet VCS (placeholder name `jj`), which has
support for octopus merges and other ways of ending up with merges of
more than 3 versions. I wanted to be able to represent such conflicts
in the working copy and therefore thought of this format (although I
have not yet implemented it in my VCS). I then attended a meeting with
Larry McVoy, who said BitKeeper has an option (`bk smerge -g`) for
showing a similar format, which reminded me to actually attempt this
in Mercurial.
Differential Revision: https://phab.mercurial-scm.org/D9551
[This file is here for historical purposes, all recent contributors
should appear in the changelog directly]
Andrea Arcangeli <andrea at suse.de>
Thomas Arendsen Hein <thomas at intevation.de>
Goffredo Baroncelli <kreijack at libero.it>
Muli Ben-Yehuda <mulix at mulix.org>
Mikael Berthe <mikael at lilotux.net>
Benoit Boissinot <bboissin at gmail.com>
Brendan Cully <brendan at kublai.com>
Vincent Danjean <vdanjean.ml at free.fr>
Jake Edge <jake at edge2.net>
Michael Fetterman <michael.fetterman at intel.com>
Edouard Gomez <ed.gomez at free.fr>
Eric Hopper <hopper at omnifarious.org>
Alecs King <alecsk at gmail.com>
Volker Kleinfeld <Volker.Kleinfeld at gmx.de>
Vadim Lebedev <vadim at mbdsys.com>
Christopher Li <hg at chrisli.org>
Chris Mason <mason at suse.com>
Colin McMillen <mcmillen at cs.cmu.edu>
Wojciech Milkowski <wmilkowski at interia.pl>
Chad Netzer <chad.netzer at gmail.com>
Bryan O'Sullivan <bos at serpentine.com>
Vicent Seguí Pascual <vseguip at gmail.com>
Sean Perry <shaleh at speakeasy.net>
Nguyen Anh Quynh <aquynh at gmail.com>
Ollivier Robert <roberto at keltia.freenix.fr>
Alexander Schremmer <alex at alexanderweb.de>
Arun Sharma <arun at sharma-home.net>
Josef "Jeff" Sipek <jeffpc at optonline.net>
Kevin Smith <yarcs at qualitycode.com>
TK Soh <teekaysoh at yahoo.com>
Radoslaw Szkodzinski <astralstorm at gorzow.mm.pl>
Samuel Tardieu <sam at rfc1149.net>
K Thananchayan <thananck at yahoo.com>
Andrew Thompson <andrewkt at aktzero.com>
Michael S. Tsirkin <mst at mellanox.co.il>
Rafael Villar Burke <pachi at mmn-arquitectos.com>
Tristan Wibberley <tristan at wibberley.org>
Mark Williamson <mark.williamson at cl.cam.ac.uk>