title: git diff renamed file
body: <p>I have a file <code>a.txt</code>.</p>
  
  <pre><code>cat a.txt
  &gt; hello
  </code></pre>
  
  <p>The contents of <code>a.txt</code> is "hello".</p>
  
  <p>I make a commit.</p>
  
  <pre><code>git add a.txt
  git commit -m "first commit"
  </code></pre>
  
  <p>I then move <code>a.txt</code> into a <code>test</code> dir.</p>
  
  <pre><code>mkdir test
  mv a.txt test
  </code></pre>
  
  <p>I then make my second commit.</p>
  
  <pre><code>git add -A
  git commit -m "second commit"
  </code></pre>
  
  <p>Finally, I edit <code>a.txt</code> to say "goodbye" instead.</p>
  
  <pre><code>cat a.txt
  &gt; goodbye
  </code></pre>
  
  <p>I make my last commit.</p>
  
  <pre><code>git add a.txt
  git commit -m "final commit"
  </code></pre>
  
  <p>Now here is my question:</p>
  
  <p>How do I diff the contents of <code>a.txt</code> between my last commit and my first commit?  </p>
  
  <p>I've tried:
   <code>git diff HEAD^^..HEAD -M a.txt</code>, but that didn't work.  <code>git log --follow a.txt</code> properly detects the rename, but I can't find an equivalent for <code>git diff</code>.  Is there one?</p>