register_klass_file (Thor)

    # File lib/thor.rb, line 106
        def register_klass_file(klass, file = caller[1].split(":")[0])
          unless self == Thor
            superclass.register_klass_file(klass, file)
            return
          end

          file_subclasses = subclass_files[File.expand_path(file)]
          file_subclasses << klass unless file_subclasses.include?(klass)
          subclasses << klass unless subclasses.include?(klass)
        end