title: GIT: <Directory> already exists in the index
body: <p>Hi I have an existing checked in directory which contains a lot of common code.</p>
  
  <p>I moved the code to an external repository and then tried to use it as a sub-module.</p>
  
  <p>The issue now is that when i try to add the sub-module, an error is thrown:  already exists. I tried multiple forums and couldn't find any resolution.</p>
  
  <p>I have already removed the original directory from the repository and then checked in the changes(removal of directory). Still the issue. some how it saying that the directory exists in the index.</p>
  
  <p>how to deal with this??</p>