title: Github pull request shows too many changes/commits
body: <p>We have two branches: <code>develop</code> and <code>master</code>.</p>
  
  <p>For some reason when I create a PR of <code>develop</code> --> <code>master</code>. It shows a whole list of previous commits and changes even if I've made only a single line change in <code>develop</code>.</p>
  
  <p>Also, it will say "Can't automatically merge" when from the command line I'm able to merge <code>develop</code> into <code>master</code> without a problem.</p>
  
  <p>Any idea what might be going on? Previously it was working fine for us.</p>
  
  <p>EDIT: Here's what it looks like when we try to merge <code>develop</code> to <code>master</code>. Only the most recent commit is new. The others were merged previously:
  <a href="https://i.stack.imgur.com/eF0b6.png" rel="noreferrer"><img src="https://i.stack.imgur.com/eF0b6.png" alt="enter image description here"></a>
  And the output of <code>git log --oneline --decorate --all --graph</code>
  <a href="https://i.stack.imgur.com/LjjRk.png" rel="noreferrer"><img src="https://i.stack.imgur.com/LjjRk.png" alt="enter image description here"></a></p>