title: Cannot find FileMerge (opendiff tool) but I have xcode 4.6 installed
body: <p>When I attempt to run FileMerge as a GUI for Opendiff, I receive an error:</p>
  
  <pre><code>$ git mergetool -t opendiff
  Merging:
  Gemfile
  Gemfile.lock
  ...
  
  Normal merge conflict for 'Gemfile':
    {local}: modified file
    {remote}: modified file
  Hit return to start merge resolution tool (opendiff): 
  2013-12-26 20:00:20.248 opendiff[22367:e07] Couldn't find FileMerge
  Gemfile seems unchanged.
  Was the merge successful? [y/n] ^C
  $
  </code></pre>
  
  <p>I have installed XCode 4.6.3 and Command Line Tools for Xcode April 2013.  I am running OSX 10.7.5 </p>
  
  <p>I have tried solutions from the following two links with no success:</p>
  
  <p><a href="https://stackoverflow.com/questions/5037230/git-diff-with-opendiff-gives-couldnt-launch-filemerge-error">git diff with opendiff gives &quot;Couldn&#39;t launch FileMerge&quot; error</a></p>
  
  <p><a href="https://stackoverflow.com/questions/9562761/is-filemerge-still-available-after-xcode-4-3-installation">Is filemerge still available after Xcode 4.3 installation?</a></p>
  
  <p>When I go to <code>Xcode -&gt; Open Developer Tool</code> I do not see <code>FileMerge</code> in the list of options.  There is a <code>More Developer Tools</code> link that takes me here: <a href="https://developer.apple.com/downloads/index.action?name=for%20Xcode%20-" rel="nofollow noreferrer">https://developer.apple.com/downloads/index.action?name=for%20Xcode%20-</a></p>
  
  <p>How do I get FileMerge working? </p>