I think one of the largest reasons for Go moving to github is that most of their...

I think one of the largest reasons for Go moving to github is that most of their community already develops there. They cited that as a reason here: https://groups.google.com/forum/#!topic/golang-dev/sckirqOWe...

Also, just because they're using git for public projects doesn't rule out that they may be using mercurial internally. Google pays a number of people to work on mercurial... I'm not sure if that's the same for git.