title: Github can't merge branch, no conflicts, manually it auto-merges
body: <p>I have a pull request that Github says it can't automatically merge. This change is behind master a few commits, but without conflicts.</p>
  
  <p>Manually merging I don't get any conflicts, and I get this output:</p>
  
  <pre><code>(on master)
  $git merge otherbranch
  [vim pops up for commit message, :wq]
  Auto-merging &lt;file&gt;
  Merge made by the 'recursive' strategy.
  &lt;file&gt; | 1 +
  1 file changed, 1 insertion(+)
  </code></pre>
  
  <p>Is that why Github can't merge automatically? It merged automatically from the command line anyway. Is this not automatic enough for Github?</p>