title: P4 merge error, No target file(s) in both client and branch view
body: <p>First of all, I have a stream root named "//streams/main".
  Then, I created a sub stream named "//streams/branchA" whose parent is "//streams/main". and I always worked on my own stream - branch A</p>
  
  <p>Now, I want to do a down integration, from main to branch A. On my dev machine, I have synced my local client to latest version of branch A. Then, I input the following command (the command was generated by the dialog of P4, Merge/Integrate, I copied it out from log window of P4)</p>
  
  <pre><code>p4 merge -c 101005 -r -S //streams/BranchA -s //streams/BranchA/...@label_20130901
  </code></pre>
  
  <p>but, I got the error</p>
  
  <pre><code>Integration errors: No target file(s) in both client and branch view.
  
  There are a total of 1 errors.
  </code></pre>
  
  <p>I don't know where I made a mistake, and how to fix it? </p>
  
  <p>My dev machine is WIN8, P4 win client version is 2013 March 20. </p>