title: Github compare two different repository from different users
body: <p>I want to compare <code>repo_a</code> from <code>user_a</code> AND <code>repo_b</code> from <code>user_b</code>. I tried to fork them but I still can't compare them!</p>
  
  <p>How can I do this? Can i do it with the Github website? I want to compare them visually, not just in a log file.</p>