Cancel release upgrade if the user boots back into their system partition

[brs17]

Cancel release upgrade if the user boots back into their system partition, instead of the recovery partition

After fetching the release upgrade packages, reboot, but boot into the system partition instead of the recovery partition.

The daemon should revert the changes made to the source lists once it realizes that the upgrade did not happen.

[brs17]

Part of canceling the upgrade should include setting the systemd-boot option. After purposefully booting into the user session instead of the recovery partition and then rebooting, the system automatically went into the recovery partition again.

[brs17]

I just noticed that the icons in the Pop!_Shop are updated to Adwaita 19.04 icons if the upgrade is canceled.

[brs17]

I think this edge case should not be a high priority at all. I am thinking that a notification that an upgrade is ready should be sufficient for pushing someone to upgrade.