It's come up a few times that people want to mark working copies other
than the current one as immutable. We don't have a way of finding such
commits. `working_copies() ~ @` is close, but it's not correct if the
same commit is being edited in the current workspace and in another
workspace. This patch adds a `other_working_copies()` revset for it.

…mits

This should avoid other workspaces going stale most of the time.

Also include all working copies in default log since we would
otherwise hide other working copies now.