Re: combined diff does not detect binary files and ignores -diff attribute

On Tue, May 24, 2011 at 09:19:43AM +0200, Michael J Gruber wrote:

quoted

It is conceivable that we _could_ newly define a "combined external diff
driver" that would take 3 or more files, and compute and show the combined
result by itself, but that will certainly not go through the codepath you
touched with the textconv patch. Calling out to such a new type of
external diff driver would have to happen at the level where we have 1+N
blob object names for a N-parent commit, namely, at the beginning of
show_patch_diff(), bypassing the entire contents of that function and
instead letting the new n-way external diff driver do everything.

I however highly doubt that such an interface would make sense. For
example, what would be the desirable format to compare three versions of
"What's cooking" postings, and how would the updated compare-cooking.perl
script would look like?

Yeah, currently --cc with external makes no sense, but there are several
external tools which could present a 3-way diff in a useful way (or even
n-way with n>3), e.g. vimdiff, kdiff3, meld.

I agree with Junio that we would need a new config option and external
interface for "n-way combined diff". However, isn't what things like
vimdiff and meld do the reverse of our combined diff? That is, don't
they assume the 3 trees are: ours, theirs, and ancestor (i.e., merge
base)? Whereas in a combined diff, it is actually: merge parent 1
(ours), merge parent 2 (theirs), and merge _result_.

Also, do those tools generally handle n-way comparisons as opposed to
3-way?

-Peff