Sync master branch of forked repo with upstream master branch

update-master-branch.sh

# Part 1, if necessary: 
# Configure a remote for your fork
# https://help.github.com/articles/configuring-a-remote-for-a-fork/

# In Terminal, cd into your local repo and run this command:
git remote add upstream https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git
# In general, git remote add upstream <upstream repo>

# Verify by running this command:
git remote -v


# Part 2: 
# Sync your fork with upstream repo
# https://help.github.com/articles/syncing-a-fork/

git fetch upstream
git checkout master
git merge upstream/master


# Part 3:
# Push changes from your local repo to remote
# https://help.github.com/articles/pushing-to-a-remote/

git push origin master
# In general, git push <REMOTENAME> <BRANCHNAME> 
# Here, 'origin' is your fork's repo on GitHub.

# Done. The master branch of your forked repo, 
# both locally and remotely, 
# is now even with the upstream master branch.

Also see https://gist.github.com/xaxim/0ad48b3afe6e81fa6097d82b22ed8cde

git fetch upstream
git checkout master
git merge upstream/master
git merge upstream/master
git commit
git push