update: add comments and test cases for updating across branches
Add comment to merge.py:update() showing various cases of 'hg update': to a
descendant, crossing named branches, and crossing branches within a named
branch; with no option, -c or -C; with or without uncommitted changes; and
with or without a specific revision. Add tests for all of these cases.
% status without inotify
A a
! b
% inserve
% status
A a
! b
? hg.pid
Are we able to kill the service? if not, the service died on some error