title: Changing github credentials
body: <p>I am a collaborater : my github account name is dave<br>
  I am also the repo owner : my github username is chief  </p>
  
  <p>I have managed to fork one of chief's projects,<br>
  commit and submit a pull request to him.  </p>
  
  <p>Now I need to accept that pull request.  </p>
  
  <p>How do I switch to chief's credentials, so that I can clone chief/projectname.git  </p>