Build numbers and git tags

Yeah, it's a bit difficult. I've been trying to tag here but I keep forgetting (and haven't pushed the tags anyway) - however if you have the build, just run it and type process.env.GIT_COMMIT (although that only works for the last few versions).

Otherwise, you can get a rough idea by doing git blame ChangeLog and finding the git commit nearest the top of the version tag you want. Then the actual build will be a little bit before that.