hg diff --branch

[Stepan Koltsov]

Hi, all.

I've just sent a patch using patchbomb extension to this mailing list.

Patch adds hg diff --branch <branch> option. Command outputs a diff
between parent of the first commit within the given branch and a
branch head.

It must be very useful in our development style: we have fixed
upstream base revision (of lighttpd) and have lots of patches stored
as separate branches started from that base. Patch branches are named,
so with this patch each feature development result can be easily
reviewed by single command: hg diff --branch my-feature .

--diff requires that branch has single head, and single parent of tails.

I did not use branchheads.cache (because it is useless without
branchtailparents.cache that I'd like to avoid).

Please, review and/or apply.

S.