Allow creating actives without an upper directory for
capturing changes. Actives without the upper directory
will always be mounted read only. Read only actives
must have a parent.
Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
With the change to the snapshotter interface, we've now updated the
overlay driver to follow the conventions of the current test suite. To
support key unification, an hashed index was added to active and
committed directories. We still need to do some testing around
collisions, but we'll leave that for a future PR.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
