title: How do I determine which changes in one branch are missing from another?
body: <p>I'm using git.  I have a branch, <code>apifixes</code>, that was branched from <code>master</code> some time ago.  Most, but not all, of the changes from the <code>apifixes</code> branch have been merged back into <code>master</code>.  At least, I believe this is the case, because when I try to do</p>
  
  <pre><code>git branch -d apifixes
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>error: The branch 'apifixes' is not an ancestor of your current HEAD.
  </code></pre>
  
  <p>How can I tell which changes are in <code>apifixes</code> but not in <code>master</code>?</p>