Hammer history security concern
Hammer history mounts allow access to deleted files.
This can be an issue if you realized that this data should not have been
available in the first place.
An alternate scenario is that group membership changed, and you don't
want the new group members to have access to past data.
I think we should address this in some sort in the release. One way is
to only allow the owner to access the snapshot, and ignore group/other
permissions on snapshots. This is probably very inconvenient,
especially for root owned system directories.
Another way would be to somehow combine current and past owner/flags,
but this is probably hard to reason about.