Git snippet to update a forked repository

update_fork.sh

# Add the remote, call it "upstream":

git remote add upstream https://github.com/whoever/whatever.git

# Fetch all the branches of that remote into remote-tracking branches,
# such as upstream/master:

git fetch upstream

# Make sure that you're on your master branch:

git checkout master

# Rewrite your master branch so that any commits of yours that
# aren't already in upstream/master are replayed on top of that
# other branch:

git rebase upstream/master

# If you've rebased your branch onto upstream/master you may need
# to force the push in order to push it to your own forked repository on GitHub:

git push -f origin master