The current release can be build from git clone sources because running git rev-parse HEAD at build time works, but it fails to build from an archive tarball such as is generated by GitHub when you download the source link on a release and generated with git archive.

This fixes that by first checking an env var that a user can set by using export TAR_COMMIT_ID=$(git get-tar-commit-id <package>.tar.gz). It isn't a pancea and requires some intervention, but at least it makes it possible to build without a patch, etc.