class Thor::Runner

def method_missing(meth, *args)


Thor::Runner is then responsible for finding the command in all classes.
If a command is not found on Thor::Runner, method missing is invoked and 
def method_missing(meth, *args)
  meth = meth.to_s
  initialize_thorfiles(meth)
  klass, command = Thor::Util.find_class_and_command_by_namespace(meth)
  self.class.handle_no_command_error(command, false) if klass.nil?
  args.unshift(command) if command
  klass.start(args, shell: shell)
end