Re: [PATCH] cherry-pick: do not error on non-merge commits when '-m 1' is specified

[Jeff King <peff@peff.net>]

On Tue, Mar 26, 2019 at 03:07:42PM -0700, Elijah Newren wrote:

> On Tue, Mar 26, 2019 at 9:35 AM Jeff King <peff@peff.net> wrote:
> >
> > On Mon, Mar 25, 2019 at 09:43:09AM +0300, Sergey Organov wrote:
> >
> > > How about changing "git show -p M" to output "diff -p M^ M" rather than
> > > "diff-tree --cc M" for merge commits? It's really surprising specifying
> > > -p has no visible effect.
> >
> > That's because "-p" is already the default, and the format selection is
> > orthogonal to the handling of merge commits. Providing "-m" would
> > actually override the "--cc" default (though "--first-parent -m" is
> > likely to be less noisy, per this discussion).
> >
> > As far as defaults go, I dunno. The idea is that "--cc" would give you a
> > nice summary of what the merge _itself_ had to touch. I think that's
> > valuable, too. If we were starting from scratch, I think there could be
> > a discussion about whether one default is better than the other. But at
> > this point I have a hard time finding one so much obviously better than
> > the other to merit changing the behavior.
> 
> Indeed, some of us would view a first parent diff default for merges
> as problematic.  However, I'd like to point out (or remind) that these
> two options aren't the only ways you could view a merge.  Thomas
> Rast's --remerge-diff[1] is another (even if not yet part of git.git).
> Gerrit uses something similar-ish for its default way of showing a
> merge.

Heh, I almost mentioned remerge-diff, but since it's not actually part
of Git, I didn't want to get into a tangent. But since you mention it,
yes, I actually find it quite a useful way of looking at the diff,
especially when I want to see what the person resolving the conflicts
actually _did_. The --cc combined diff is too eager to throw away hunks
that resolved purely to one side (which _most_ of the time is what you
want, but when you're hunting a possible error in the merge, it's quite
confusing).

How close is merge-recursive.c to actually doing a pure in-memory merge?

I seem to recall that was a (the?) sticking point for the original
remerge-diff.

-Peff