title: GitHub - only allow pull request
body: <p>I have a public github repo and want to disallow other users to merge into the master branch. They should only be able to create other branches and create pull request. I'm the only one who accept and merge pull requests. </p>
  
  <p>Is this possible with GitHub and if yes, how can I set this up?</p>
  
  <p>Kind regards</p>