title: `git-p4 clone` fails "new tip ... does not contain ..."
body: <p>I'm runnining on Windows, with the windows p4 client, and git installed via Cygwin. The p4 client advertises how its syntax is regular across platforms and all that, so that should be hunky-dory.</p>
  
  <p>So when I go to <code>git-p4 clone --verbose //depot/path/to/source</code>, it lists out all the files in the repository as though they were being checked out, then dies saying </p>
  
  <blockquote>
    <p>Exception: fast-import failed: warning: Not updating refs/remotes/p4/master (new
     tip cd601b92da8625c90af05685e450e55b6d19c9e9 does not contain 3a512c9408e3cbeef
    94c78dfd7115f81e4a6fd0d)</p>
  </blockquote>
  
  <p>and concludes with a big block of "git-fast-import statistics". Looking at the error: new tip? Huh? What needs to contain it?</p>
  
  <p>What I'm left with is a .git repo that's a couple of megs (much, much smaller than the full source tree would be). Any ideas?</p>