TODO
(No diagram for downgrading yet.)
Downgrading is generally unsafe, here's the sequence of calls when every script succeeds:
1.2-4->prerm upgrade 1.2-3 1.2-3->preinst upgrade 1.2-4 Files are unpacked 1.2-4->postrm upgrade 1.2-3 1.2-3->postinst configure 1.2-4 This is the same procedure as upgrading, but swapping versions.