From inside the forked repository, add a new remote
pointing to the upstream repo:
$ git remote add upstream git://github.com/upstream/repo.git
Then change the master branch to track upstream/master
.
$ git checkout -b anything
$ git branch -D master
$ git checkout --track upstream/master
$ git branch -D anything
$ git pull
$ git checkout -b new-changes
$ # make bump changes
$ git commit
$ git push --set-upstream origin new-changes
$ # make PR from browser
$ # wait for PR to be merged
$ git checkout master
$ git branch -D new-changes