What a pain. It turns out that github.run_number is counting the number of
times a specific workflow has been run - but that's different for different
workflows, so using that won't get us a single tag with all the corresponding
build artifacts. And sadly I can't find a simple atomic way to increase a
GitHUb repo variable, so I came up with this somewhat convoluted dance, using
the the fact that a push to an existing brach that isn't a fast-forward will
fail.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
94c47f64ac