title: git-flow is giving error: An item with the same key has already been added
body: <p>I'm running a git-flow process through source tree, trying to finish my branch. I get this error:</p>
  
  <pre><code>sh.exe "C:\Program Files\Git\usr\bin\git-flow" feature finish -k XXX
  fatal: ArgumentException encountered.
     An item with the same key has already been added.
  
  fatal: ArgumentException encountered.
     An item with the same key has already been added.
  </code></pre>
  
  <p>Strangely enough, this happens against two different repo's.</p>
  
  <p>Any suggestions?</p>
  
  <p>More information: Using "git extensions" I was able to finish the both branches. I believe they were both created from source tree though.  The difference is, it seems source tree using git-flow, whereas git extensions seems to use "git flow"</p>