title: Need to handle git-submodules in git-archive
body: <p>I need to pack git submodules inside of tarball which I create with <code>git-archive</code>.</p>
  
  <p>I see that in 1.6.5 <code>git-archive</code> does not support git submodules.</p>
  
  <p>I see several scripts to handle this case in the net, but I'm not sure which one to pick.</p>
  
  <p>What is the best / most official way to do this?</p>