This patch series builds on 1ef8b72a7f87afe7cffe52393d99e1b14e4770e1 to add two new 'guix system' actions: roll-back and switch-generation.
I've verified that both 'make check' and 'make check-system' pass (with the exception of the system tests 'nss-mdns' and 'encrypted-root-os', which both fail on my system even without my patches). I've manually verified the following for a VM with a single disk and single partition, as well as for a VM with multiple disks and the store on a separate partition: * The grub.cfg file that 'roll-back' and 'switch-generation' generates looks correct and is correctly registered as a GC root. * The system can boot after 'roll-back' and 'switch-generation', the default entry is correct, and the resources necessary for the GRUB theme are loaded without error. * Any attempt to switch to a nonexistent generation fail, regardless of whether a relative or absolute generation spec is used. * The existing 'list-generations' command continues to show the generations correctly, even after switching generations. Hopefully everything is OK this time! Thank you for taking the time to review it. -- Chris