How to update a GitHub forked repository?

In your local clone of your forked repository, you can add the original GitHub repository as a “remote”. (“Remotes” are like nicknames for the URLs of repositories – origin is one, for example.) Then you can fetch all the branches from that upstream repository, and rebase your work to continue working on the upstream version. In terms of commands that might look like:

# 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. You’d do that with:

git push -f origin master