Currently --nofilesystem just means that we undo a similar --filesystem,
so --filesystem=~/foo/bar --nofilesystem=~/foo/bar means we can access foo.
If you did --filesystem=~/foo --nofilesystem=~/foo/bar then the later
would have no effect.
We now handle this by giving access to foo, but hiding bar beneath it.
Closes: #1245
Approved by: alexlarsson