title: Is there a way to add a submodule to a git repo that share a directory structure
body: <p>I have a repo with a directory structure like so
  <code>
      /foo
      /foo/bar
      /foo/bar/me
      /foo/bar/you
      /foo/one
      /foo/one/two
      /foo/one/three
  </code></p>
  
  <p>There is a submodule I want to add that has this structure
  <code>
      /foo/bar/file.txt
      /foo/one/otherfile.txt
  </code></p>
  
  <p>Is there way to add that submodule to my repo, where the submodule shares some of the same directory structure?
  I've tried using the basic add submodule commands, but I get the error that <code>'foo' already exists in the index</code>, which I take to mean that becuase my repo already has a /foo directory, it can't add the submodule with the same directory.</p>
  
  <p>Is there anyway to have the submodule share the directory structure, but still have different files?</p>