Comment 26 for bug 45719

>1) We need to have whitebox testing of WT.update in workingtree_implementations. This is updating the api to allow a 'revision' parameter, and we should make sure all implementations continue to do so.

>2) We need a NEWS entry describing the API break (as plugins that implement a WT will now need to accept a revision in their update
function.)

>3) You are using "revision[0].in_history(branch).rev_id" which should be replaced with "revision[0].as_revision_id(branch)". The latter is a newer function that doesn't have to do as much work in most cases.

I've done these three in my attached branch, except that as_revision_id apparently can't be used in both cases, because we rely on the side effect of in_history checking it's really in the repository.