Re: [PATCH 7/7] xdiff: make diff3 the default conflictStyle

On Fri, Jun 11, 2021 at 10:32 AM Felipe Contreras
[off-list ref] wrote:

Elijah Newren wrote:

quoted

On Fri, Jun 11, 2021 at 7:25 AM Felipe Contreras [off-list ref]
wrote:

quoted

quoted

Personally I have never experienced what you posted, so maybe there's
something else happening behind the scenes.

Maybe merge-ort changed something.

merge-ort made no changes relative to content merges or choice of merge
bases.  (In fact, merge ort doesn't even handle content merges; that's the
xdiff layer.)  Even if merge-ort had made changes in this area, merge-ort
is not the default and I didn't see the necessary config tweaks in your
list of config options.  (I would have recommended against people using
merge ort until 7bec8e7fa6 ("Merge branch 'en/ort-readiness'", 2021-04-16),
which only made it into a release last week with 2.32.  I probably won't be
recommending it as the default at least until the optimization work is
merged and it's hard to predict how many more months that will take.)

Indeed, I tested on v2.25 and found the same output.

I thought of merge-ort because 1) I've never seen such kind of output
before, and 2) grepping the code I thought I saw merge-ort being the
default of something, but now I seem to be unable to find where.

We have briefly discussed multiple times what things might be needed
to eventually make merge-ort the default (though it's not even
complete yet; I'm five months into upstreaming the optimization
patches with an unknown number of months left).  There were also a
couple patches to make the _tests_ default to using merge-ort on most
platforms, while still keeping one suite that tests merge-recursive to
ensure we don't add breakage.  Perhaps one of those is what you're
thinking of?

quoted

It's more likely that the codebases you work with just don't have
criss-cross merges.

Yes, that's it.

I don't see why people in these kinds of codebases would like diff3
doing that by default.

I suspect they don't[1].  What's the alternative, though?  Not using
diff3?  Picking a different base to avoid the occasional nested
conflict in the inner merge region, but which overall has much worse
other side effects?  I think Junio was addressing this when he
recently said elsewhere in this thread that "Rejecting diff3 style
output because of the way a conflicted part in the inner merge appears
as a common ancestor version may be throwing the baby out with the
bathwater"[2].  Sure, it's an annoyance, but diff3 is still a good
option and there is no current solution to the annoying nested merge
display.

Also, not sure whether it matters or not, but just for completeness I
should point out that you can get nested conflict markers without
criss-cross merges and without merge.conflictStyle=diff3.  It's just
much more rare.

[1] https://lore.kernel.org/git/CAPc5daUC+6cHpexXTO24p4mG_5eL1JmxrYm8h3UfdTh_FMka=w@mail.gmail.com/ (local)
[2] https://lore.kernel.org/git/xmqqh7i5ci3t.fsf@gitster.g/ (local)