title: Git will not init/sync/update new submodules
body: <p>Here's part of the contents of my <code>.gitmodules</code> file:</p>
  
  <pre><code>[submodule "src/static_management"]
          path = src/static_management
          url = git://github.com/eykd/django-static-management.git
  [submodule "external/pyfacebook"]
          path = external/pyfacebook
          url = http://github.com/sciyoshi/pyfacebook.git
  </code></pre>
  
  <p>However, <code>.git/config</code> only contains the first:</p>
  
  <pre><code>[submodule "src/static_management"]
          url = git://github.com/eykd/django-static-management.git
  </code></pre>
  
  <p>The second submodule (<code>external/pyfacebook</code>) was added by another developer in a feature branch. I've inherited the development now, and have checked out the feature branch. However, Git will not pull the submodule for me. I've tried:</p>
  
  <ul>
  <li><code>git submodule init</code></li>
  <li><code>git submodule update</code></li>
  <li><code>git submodule update --init</code></li>
  <li><code>git submodule sync</code></li>
  <li>Removing all submodule definitions from <code>.git/config</code> and running <code>git submodule init</code>. It only copies over the previously existing submodule and ignores the new one.</li>
  <li>Entering new submodule definitions in <code>.git/config</code> manually and running <code>git submodule update</code>. Only the previously existing submodules bother to update.</li>
  </ul>
  
  <p>in various combinations, but git simply will not update <code>.git/config</code> based on the new contents of <code>.gitmodules</code>, nor will it create the <code>external/pyfacebook</code> folder and pull the submodule's contents. </p>
  
  <p>What am I missing? Is manual intervention (adding a submodule entry by hand to <code>.git/config</code>) truly required, and why?</p>
  
  <p><strong>Edit:</strong> Manual intervention does not work. Manually adding the new submodule entry to <code>.git/config</code> doesn't do a thing. The new submodule is ignored.</p>