Git: Update from Upstream (for SilverStripe3.0 contributions)

In terminal
git fetch upstream && git checkout master && git rebase upstream/master
git fetch upstream && git checkout 3.0 && git rebase upstream/3.0
git fetch upstream && git checkout 3.1 && git rebase upstream/3.1

Or, on a branch:
git fetch upstream && git rebase upstream/master
git fetch upstream && git rebase upstream/3.0
git fetch upstream && git rebase upstream/3.1

To push the update to your github account:
git push origin master