Re: feature suggestion: optimize common parts for checkout --conflict=diff3

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> I'm not sure I agree. In this output (which does the zealous
> simplification, the splitting, and arbitrarily assigns deleted preimage
> to the first of the split hunks):
>
>   1234A<B|56=X>C<D|Y>E789
>
> I do not see the promotion of C to "already resolved, you cannot tell if
> it was really in the preimage or not" as any more or less misleading or
> wrong than that of A or E.  It is no more misleading than what the
> merge-marker case would do, which would be:
>
>   1234A<B=X>C<D=Y>E789

That is exactly my point and I think we are in complete agreement.
While the intended difference between RCS merge and diff3 -m is for
the latter not to lose information on the original, zealous-diff3
chooses to lose information in "both sides added, identically" case.

Where we differ is if such information loss is a good thing to have.

We could say "both sides added, identically" is auto-resolved when
you use the zealous option, and do so regardless of how the merge
conflicts are presented.  Then it becomes perfectly fine to eject
"A" and "E" out of the conflicted block and merge them to be part of
pre/post contexts.  The same goes for reducing "<C|=C>" to "C".  As
long as we clearly present the users what the option does and what
its implications are, it is not bad to have such an option, I think.

> The wrong thing to me is the arbitrary choice about how to distribute
> the preimage lines.

Yeah, but that is not "diff3 -m" vs "zealous-diff3" issue, is it?
If you value the original and want to show it somewhere, you cannot
avoid making the choice whether you are zealous or not if you split
such a hunk.