The gist of this action is upgrading the specified aport to the latest
version. There are implementations for both stable packages (which check
via the release-monitoring.org API for new versions) and git packages
(which check the GitLab/GitHub API for new commits on the main branch).
There's also the possibility to pass --all, --all-stable & --all-git to
the action which either loops through all packages, or just stable or
git packages and upgrades them.
The --dry argument is also respected.
Note, that the implementation does update the variables pkgver, pkgrel
and _commit but it doesn't update the checksums because that would slow
down the process a lot, and is potentially undesirable.
