title: git diff-tree shows a delete but there's no delete in git log
body: <p><code>git diff-tree</code> indicates a file was deleted but when I run <code>git log</code>, it doesn't show anything.</p>
  
  <p>To wit:</p>
  
  <pre><code>&gt; git diff-tree --stat --summary 1990ca669fe..00de228dcdc -- t/tests.conf
  t/tests.conf |    9 ---------
  1 files changed, 0 insertions(+), 9 deletions(-)
  delete mode 100644 t/tests.conf
  </code></pre>
  
  <p>And when I run:</p>
  
  <pre><code>&gt; git log 1990ca669fe..00de228dcdc -- t/tests.conf
  </code></pre>
  
  <p>I get no output.  </p>
  
  <p>Any idea I on how I can track down why git thinks this file has been deleted since it's also causing problems in a merge I'm trying?</p>
  
  <p><strong>Update</strong></p>
  
  <p>This doesn't produce any output either:</p>
  
  <pre><code>&gt; git log 1990ca669fe...00de228dcdc -- t/tests.conf
  </code></pre>
  
  <p>And the commits are reachable:</p>
  
  <pre><code> &gt; git rev-list 00de228dcdc | grep 1990ca669fe
    1990ca669fe9ec94d215945388458daba8d94747
  </code></pre>