Just as a curiosity thing, how does gpm figure out about plugin updates?
By default GPM has a 24 hour cache where it grabs a JSON file from the Grav site (when you run bin/gpm) and compares the versions in that file with the versions installed. You can force gpm to grab a fresh copy with -f appended to the commands.
Gotcha… and how does the JSON file get updated? Some automated job, or does somebody have to inform you of an update?
Yah, we have a custom Grav CLI command that runs as a cron job every hour. This takes a list of all known plugins/themes/skeletons and goes and grabs their appropriate blueprint information from GitHub.