title: merge /discard reports 'No Pending Changes' when /candidate shows them
body: <p>I'm trying to run a <code>merge /discard</code> command (<code>tfs merge /discard /version:nnn:yyy $/sourceproj $/targetproj /recursive</code>) but it says there are no pending changes.</p>
  
  <p>If I run a <code>tfs merge /candidate $/sourceproj $/targetproj</code> it shows the relevant changesets as candidates.</p>
  
  <p>any ideas why this happens and how to get round it? </p>
  
  <p>Thanks. </p>