publish-package.sh now checks the Forgejo package listing first and
exits early if the current version is already published, instead of
failing with a 409 on the first upload attempt. Also generates a
changelog (git log since whichever previous package's embedded
short-sha we can find) and attaches it both inside the tarball
(MANIFEST.txt, CHANGELOG.txt) and as its own uploaded file, so anyone
browsing the package page can see what changed without downloading
the archive.
891383bf7b