Before sending Pull Requests to the the quickstart org (upstream branch) make sure that your branch is in sync. To do so, you will add the upstream branch to your fork.
List remotes.
git remote -v
You should see following output.
origin git@github.com:avattathil/quickstart-linux-bastion.git (fetch)
origin git@github.com:avattathil/quickstart-linux-bastion.git (push)
Add upstream and fetch the commits from the remote.
git remote add upstream git@github.com:aws-quickstart/quickstart-linux-bastion.git
git fetch upstream
From github.com:aws-quickstart/quickstart-linux-bastion * [new branch]......develop..........................-> upstream/develop * [new branch]......master...........................-> upstream/master