title: git submodule modified files status
body: <p>I've added a submodule in my main git folder tree and haven't changed anything but it's showing up modified.  What do I do about this?</p>
  
  <pre><code>$ git status
  # On branch master
  # Changed but not updated:
  #   (use "git add &lt;file&gt;..." to update what will be committed)
  #   (use "git checkout -- &lt;file&gt;..." to discard changes in working directory)
  #
  #    modified:   example.com/soundmanager
  #
  no changes added to commit (use "git add" and/or "git commit -a")
  </code></pre>
  
  <p>I've tried a git submodule update, but it doesn't do anything.</p>