title: If you add a collaborator to a github public repo can they delete or damage anything?
body: <p>We are setting up a open source project which we would like to allow freelancers to develop alongside us without damaging anything.</p>
  
  <p>In general can the collaborators make changes to repositories without admins being able to check the changes over before code is merged into master.</p>
  
  <p>What is the best method to use to prevent the repository from user damage  whilst working with a large number of public freelance developers / users?</p>