An apply leaves every release folder it emptied standing where it was: the
live library run left 1675 husks at the root. sweep takes the same journal
and deletes only folders it can prove this run emptied - a journalled move
out of the folder or something under it, nothing but empty directories left,
no journalled destination beneath it, not a folder the run created. A folder
nobody moved cannot be selected at all, so a hand-made placeholder survives,
and a symlink anywhere inside disqualifies the subtree. Every rmdir is
journalled, so rollback recreates what a sweep removed.
Frank
1cb28095a7