Re: 3-way merge mode

[Kai Willadsen <kai willadsen gmail com>]

On 17 September 2012 23:02, Tomek Bury <tomek bury gmail com> wrote:
> Hi,
>
> Meld has got a very nice 3-way merge mode. It's activated when the 4th
> file name is passed in. In git-speak it looks like this:
>
> meld $LOCAL $BASE $REMOTE $MERGED
>
> Is there any reason why this mode is not advertised on you web site,
> missing from the man page and "meld --help"?

Not really, sort of and kinda, in that order.

Auto-merge mode was added by Piotr Piastucki a while back, and it
filled an important hole in Meld's functionality. The main reason that
it's not properly advertised is that it's not *quite* finished. By
that, I mean that while it works --- and works well! --- it has some
usability issues and could be better integrated into the existing
code-base. Of course, none of this is a criticism of Piotr's work,
which is awesome and very much appreciated. It's just that it's a lot
of work to integrate a new feature into an old code base.

I'd love merge mode to become a first-class citizen, so here is a
short (and probably incomplete) list of things-that-want-fixing:

 * The UI code for merge mode (in filemerge.py) is *tiny*, but works
by digging into some internals of FileDiff, which has caused issues in
the past. Can this be cleaned up and integrated better? (e.g., since
this was written, Meld gained support for an 'out file'... can we
replace some of the buffer-shuffling with that?)

 * The command line invocation seems arcane to me... personally, I'd
never remember the file order. An explicit flag version would be nice,
and I'd feel much better about documenting something like "meld a b c
--output d --auto-merge"; the four-argument version is then just an
alias. This would also clean up some icky code in MeldWindow.

 * There is no GUI way of starting a merge. This is hard, since the
"New comparison" dialog has been up for replacement for a *long time*.
The easiest way to proceed here would probably be a "New auto-merge"
menu entry or something, side-stepping the problem.

If anyone wants to try and make this happen, please let me know! I'm
very happy to guide people around the code base and help out where I
can... I'm just probably not going to have time to do them myself.

cheers,
Kai