support upgrading from edge to the systemd channel
moving from edge to systemd is now possible since we're currently using systemd with split /usr.
The process is pretty simple and can be done by hand, but still easy to get wrong or break due to network issues. So let's add support for it via postmarketos-release-upgrade. The steps done are:
- update mirror
apk upgrade -a- install postmarketos-base-systemd
systemctl preset-all && systemctl --user --global preset-all
The reboot command at the end fails since it's now implemented by systemd which tries to do stuff and can't because it's not running. Not sure how best to handle this, doing reboot -f instead is probably(?) fine?
Demo: pmos-upgrade-to-systemd