title: git submodule update ignores .gitmodules
body: <p>I have a git repo which has a submodule. The contents of the .gitmodule file for the main repo are:</p>
  
  <pre><code>[submodule "wits-mercuryAPI"]
      path = wits-mercuryAPI
      url = https://github.com/myorganization/wits-mercuryAPI.git
  </code></pre>
  
  <p>I would expect that when I issue the command...</p>
  
  <blockquote>
    <p>git submodule update</p>
  </blockquote>
  
  <p>... it would correctly clone the submodule from the location specified in the url of the .gitmodule file. However, it apparently tries to use an older version of this file where the url points to an incorrect url, and therefore fails.</p>
  
  <p>For the life of me I can't figure out why it behaves this way or what magic hidden property is telling this command to access some older and invisible version of the .gitmodules file.</p>