Most of the brains in this buildpack are shamelessly copied from Leafo's version, but it has some differences:
This buildpack uses openresty directly, rather than a buildpack that installs lua, and then using a template for your project
This builds Openresty and LuaRocks from source, so in some sense it's easier to update when there are new releases
Usage of the buildpack itself is pretty straighforward:
heroku buildpack:set https://github.com/geoffleyland/heroku-buildpack-openresty
Actually getting things to work takes a little longer - it's easier to use this project template.
Copy the snippet above into CLI.