title: Swift 3 / Xcode 8 Upgrade - 100's of DerivedData files missing from working copy errors
body: <p>I have just upgraded to the latest Beta version of XCode and Swift but after using the converter my app project now has over 200 build time yellow errors all stating /"projectDirectoy"/DerivedData/XXXXXXXXX/XXXX/XXX/xXXX/xXX is missing from working copy... where by the XXXXX's represent various file paths in the DerivedData folder.</p>
  
  <p>I have tried deleting the DerivedData folder from the location mentioned in the errors. </p>
  
  <p>I have tried deleting everything in the DerivedData folder in ~/Library/.</p>
  
  <p>I have tried multiple times to clean the project, reboot and do a fresh build.</p>
  
  <p>I have tried turning off source control in preferences but I don't see why I should turn this off as it was on before I updated so I want it left on.</p>
  
  <p>These errors just won't seem to go away.</p>
  
  <p>Any ideas?</p>