They don't have versions at all. It's mainly a git plugin implemented as a single shell script (plus some contrib scripts).

I've already submitted an issue with the project to add versions and git tags that the formula could point to. As a temporary measure, I pointed the url to the current head revision in an effort to not have the main url simply pull latest. Is that not advised? The revision sha as listed is current HEAD, so I could drop the revision specifier.