On Tue, May 24 2022, Junio C Hamano wrote: > Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> writes: > >> I.e. the "right" thing to do in this case would require a much more >> involved fix. We've somehow ended up not supporting --output=<file>, -I >> and probably many other options in the combined-diff mode, which both in >> testing and in this part of the implementation seems to have become an >> afterthought. > > OK, a hopefully final question. > > How much less involved is it to add a new code (without doing > anything in this patch) ...yeah, I think for this one it makes sense to narrowly focus on the segfault... > to detect and die on the combination of > combined-diff with these two options, so that we can document the > fact that we do not support them? It would give us much better way > forward than leaving the command silently ignore and give result > that is not in line with what was asked, wouldn't it? That way, the > much more involved "fix" will turn into a change to add a missing > feature. I think not much, it's rather trivial for the case where we invoke "git diff", I.e. just adding something to the "builtin_diff_combined()" branch in builtin/diff.c to detect these two cases specifically. I haven't looked in any depth into how we might reach code in combine-diff.c through other means, and if any of it can set these two indirectly somewhere else (i.e. other things that take diff options). I also wonder if I'm just wrong in my assessment that it's a Bad Thing that we take some of these without ever doing anything with them in some modes, e.g.: git log --oneline -I foo This will never do anything with that "-I foo" by definition, but would as soon as you add -p, should we error without -p (or other diff-showing options). The same goes for range-diff, format-patch, --remerge-diff and any number of other things where we take the full set of options, but only do something with a limited subset of them. It is helpful in some cases if we were more anal about it, e.g. when I was wondering why -I didn't do anything with the combined diff, but also handy for scripting and one-liners if you can tweak the command-line back & forth without it being so strict. So I don't know. Maybe I'm just trying to talk myself out of pulling on that (bound to be long) thread, but I'm coming more around to this just being a non-issue beyond the narrow and needed fix for diff_free() in particular. I.e. the more general approach of chasing down options that don't do anything for a given "diff mode". We might still want to error on some particular ones, such as -I with the combined diff (but not with --oneline, or whatever).
