Git: diff branch against master

Compare feature branch changes with upstream:

git diff $( git merge-base master HEAD )

Thanks Bill!

Update your git fork from the upstream project

Once:
git remote add upstream https://github.com/otheruser/repo.git

Every time:
git fetch upstream
git checkout master # your fork
git merge upstream/master

# Do not do this if your repo has more than one user:
git reset --hard upstream/master
git push --force origin master

(source)

Git set upstream

git branch --set-upstream-to

Or in later versions:

git branch --set-upstream

Thanks