This creates a archive-z2 repo, pull-locals it to bare-user and then
again back to archive-z2 making sure things fsck along the way.
Then it checks out all repos and makes sure each one reproduces
the same result.
Unfortunately we can't install this as a real test because
it doesn't work in the test-runner because tmpfs doesn't support
user xattrs.
https://bugzilla.gnome.org/show_bug.cgi?id=741125