title: Rename a git submodule
body: <p>Is there some easy way to rename a git submodule directory (other than going through the entire motion of  <a href="https://stackoverflow.com/questions/1260748/how-do-i-remove-a-git-submodule">deleting</a> it and re-adding it with a new destination name). </p>
  
  <p>And while we are at it, why is it that I simply cannot do the following in the parent directory: <code>git mv old-submodule-name new-submodule-name</code></p>