As far as I know the only way to achieve this using GitHub's web interface is creating a reverse pull request. This however comes at the cost of an additional merge commit which is usually not desirable as it sums up and new pull requests from B
to A
will include all those unneccesary commits.
It probably is possible to use the „Git Data“ API to merge some branches, but it is easier and safer to do it on the command line.
The strategy I recommend to others is this one:
- Never ever modify your
master
or whatever the mainline branch is called - Base your pull request branches on your
master
- Whenever there are changes to the upstream
master
integrate them by fast forwarding yourmaster
to the upstream one.
That way your pull requests will stay nice and clean and you won't have issues with rejected commits popping up in subsequent pull requests.