bad assertions in WorkingTree4._add

 affects bzr
 status confirmed
 importance medium

Originally reported by Blake Winton:

> @needs_tree_write_lock
> def _add(self, files, ids, kinds):
> """See MutableTree._add."""
> state = self.current_dirstate()
> for f, file_id, kind in zip(files, ids, kinds):
> f = f.strip('/')
> assert '//' not in f
> assert '..' not in f

Those assertions are wrong; it's fine to add a file whose name is eg
'a...t'. Also in any case they should not be raising AssertionError for
bad input data.

This is hard to reproduce from the command line but can be reproduced
from svn2bzr.