Create a tag-test-deploy workflow for releases

Observed behaviour

Releases have to be done by hand. Eww, hands.

Expected behaviour

The release manager tags a commit he wants to release and the CI/CD service (Travis) tests the code and deploys a source ball to PyPI.

To make things easier, the setuptools_scm package is used to determine the version from a Git tag automatically, so you don’t have to change any number anywhere else (so much easier!).

Resources and exact process needed to replicate

I’d point to https://github.com/fonttools/ttfautohint-py/blob/master/.travis.yml for an example, but that one is a bit complicated due to building a special binary wheel. I think you get the idea from the last deploy: thing though.

[anthrotype]

another thing that setuptools_scm does besides computing a version string from the git tags, is using git to get the list of all the files under version control and use that to automatically make the manifest for the source distribution package. No need to manually update the MANIFEST.in with weird globs. Git knows already.

[madig]

Wargh. I forgot the automatic deploy step.