title: format-patch for a single file
body: <p>I have a file called test_module.c that has some differences that I want to apply to my local working copy.</p>
  
  <p>I tried to create patch file from the remote by doing the following. However, git didn't complain about any errors. And didn't create any patch file either.</p>
  
  <pre><code>git format-patch master/dev_branch test/test_module.c
  </code></pre>
  
  <p>It is possible to create a patch of a single file, that I can apply?</p>
  
  <p>(Using git version 1.7.5.4)</p>