Default "hg branch" is equivalnt to "hg branch -r ."
Branch of some other REV is "hg branch -r REV"
Actually, what I really want is this in revsets: "hg log -r "branch_of(.)"
Then I could do: hg log -r "max(ancestors(.) and not branch(branch_of(.)))"
- the most recent ancestor on a different branch
Ah: matching (just not in the version a work). But it is not quite on... it returns revs, not branch