Re: help understanding git diff output

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

Eugene Sajine <euguess@gmail.com> writes:

> I get empty diff when i execute:
>
> $git diff branch1..branch2
>
> and i also get empty diff when running
>
> $git diff branch2..branch1

The thing is, "diff" is about comparing "two endpoints".

We still do support, as a backward compatibility measure, the A..B
notation to help people who learned "git diff" from ancient documents, and
we don't plan to deprecate the notation in any way, but don't be fooled by
the notation which usually means "the range from A to B".  In the context
of diff, it does not mean a range, as diff is about two "endpoints".

> What i cannot wrap my mind around is why the command below with
> symmetric difference range gives me non-empty diff
>
> $git diff branch1...branch2

"git diff A...B" is a short-hand for "git diff $(git merge-base A B) B",
naming the fork point between branches A and B as one end, and B as the
other end, of the diff.  Again, diff is about two "endpoints", and the
notation does not mean a symmetric difference range.