Re: help understanding git diff output

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 27, 2011, 23:05 UTC
Message-ID: <7vk4hqgd71.fsf@alter.siamese.dyndns.org>
In-Reply-To: <AANLkTi=H1LuGfQC8+u83So+6XyOqJxHJ3zsdgs4JTdkc@mail.gmail.com>

Eugene Sajine <euguess@gmail.com> writes:

Show 7 quoted lines

> 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.