code: public File getFileFromModifiedFilesNotUpdated(int index) {
      CheckUtilities.checkIntIndexInListRange(modifiedFilesNotUpdated, index);
      return modifiedFilesNotUpdated.get(index);
    }
docs: Returns the name of the file that is existing in the repository and has been locally modified.
  This file is one of the files that has been locally modified and is located at given index in
  the list.
  
  @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