title: git add in Xcode generates com.apple.dt.IDESourceControlErrorDomain error -70
body: <p>I can 100% reproduce this - if I clone a repository, drag and drop a couple of files into the cloned directory then add them to the Xcode project, then Xcode will correctly put an A status flag next to them.
  But then if I select the new files and do Source Control/Commit Selected Files I get this error:</p>
  
  <p>"The operation couldn't be completed. (com.apple.dt.IDESourceControlErroDomain error -70).</p>
  
  <p>Has anybody else seen this or know what the problem is?</p>