Update the comment fork without using Pull Requests

[almost]

See the answer on SO here: http://stackoverflow.com/a/27762278/65130

We're currently doing number 3 but number 1 would be way better and probably much more reliable.

[milessabin]

Great news ... presumably it also means it's possible to pull a branch from a fork repo without having to add that repo as an additional remote? Is so that's pretty handy :-)

[almost]

Seems like that would be possible. It is undocumented behaviour which is slightly worrying, but hopefully they won't remove it (and we can keep around the code for the other method in case they ever do).