title: Replace visual studio 2012 Diff tool with winmerge when using Microsoft Git Provider
body: <p>I have a Visual Studio 2012 v3 and git extensions installed.</p>
  
  <p>I want to change the default merge tool to winmerge but it seems that this is not a trivial task when Microsoft Git Provider is chosen.</p>
  
  <p>When i go to VS -> Tools -> Options -> Source Control I have only Plug-in-Selection tab and cannot choose configure tools to change to WinMerge.</p>
  
  <p><img src="https://i.stack.imgur.com/HDbuN.png" alt="Screenshot"></p>
  
  <p>Is there any way of using Git Extensions with WinMerge inside VS2012?</p>