code: public File getFileFromUntrackedFiles(int index) {
      CheckUtilities.checkIntIndexInListRange(untrackedFiles, index);
      return untrackedFiles.get(index);
    }
docs: Returns the name of the file at the specified index that has been created locally but has not
  yet been added to the repository by &lt;git-add&gt;.
  
  @param index
  Index in the list must be positive and less than the number of new files to commit
  @return the name of the file