No github was the location of all development from April 2008 ( see Ruby on Rails — Rails premieres on GitHub) they just didn't use pull requests. The first version of pull requests was pretty simple. I forget the details (I think in those days all you could do was do the merge or refuse it - no discussions etc) but it wasn't until they revamped pull requests (https://github.com/blog/712-pull-requests-2-0) that rails started using them