How to update a fork from the original repository

(source)
(more info)

1. [preparation] Clone your fork to have a local copy:

git clone git@github.com:YOUR-USERNAME/YOUR-FORKED-REPO.git

2. [preparation] Add remote from original repository in your forked repository:

cd into/cloned/fork-repo
git remote add upstream git://github.com/ORIGINAL-DEV-USERNAME/REPO-YOU-FORKED-FROM.git
git fetch upstream

3. [routine] Update your (local) fork from original repo:

git pull upstream master

4. [routine] Update your fork's remote:

git push origin master