def obsolete_files
      out = (existing_files - new_files - new_dirs + replaced_files).to_a
      Jekyll::Hooks.trigger :clean, :on_obsolete, out
      out
    end
def obsolete_files
      out = (existing_files - new_files - new_dirs + replaced_files).to_a
      Jekyll::Hooks.trigger :clean, :on_obsolete, out
      out
    end
Private: The list of files and directories to be deleted during cleanup process

 Returns an Array of the file and directory paths