The prepare step (installing packages etc.) normally runs on every build. With cache-after-prepare: true, the action shuts the VM down cleanly after prepare has finished, caches the prepared VM image, and boots the VM again before run. Later runs with the same prepare script restore the prepared image, skip prepare entirely, and start directly at run
https://github.com/vmactions/blissos-vm#10-cache-the-vm-image-after-prepare
Full Changelog: v1...v1.0.1