Saving things before throwing over the wall in pass4

Foreach s.file in RESYNC {
	if (l = key_init(s.file in Repository) {
		clean || abort
		add l->sfile to backup list
	}
}

flush
bk sfio -o < backuplist > BitKeeper/tmp/backup.sfio
foreach s.file in backup list {
	rm_sfile(s.file)
}

foreach file in RESYNC {
	copy to Repository
	add to applied list
}

if bk check fails
	foreach file in applied list {
		rm_sfile($file)
	}
	sfio -i < BitKeeper/tmp/backup.sfio
	bk -r check -a
	if this exits 0, then remove the backup.sfio
	else {
		tell them that it is there and how to apply it
	}
} else {
	blow away RESYNC tree
}

rm_sfile(s.file) {
	unlink(s.file)
	if emptydir(SCCS) {
		unlink(SCCS)
		try unlink parent.
		etc.
	}
}