How to merge in upstream

I.e. how to fetch changes from the remote upstream project repository and merge it to the gerrit repository.

One-off:

git remote add github https://github.com/stts-se/pronlex.git
git remote rename origin gerrit

At merge time:

git checkout master
git fetch --all
git pull
git push gerrit github/master:upstream
git checkout -b $(date --iso)-merge-github
git merge gerrit/upstream
git review -R