Comment 6 for bug 1535900

Yes, disk_format == os_tarball and container_format == bare.

At the moment, though, I'm just speaking for myself, I'm not sure what the wider Glance community will think of the 'os_tarball' identifier, though it seemed pretty clear from the discussion yesterday that 'tar' is going to confuse people, so we'll definitely want something other than 'tar'.