class Thor

def dispatch(meth, given_args, given_opts, config) #:nodoc:
  # There is an edge case when dispatching from a subcommand.
  # A problem occurs invoking the default task. This case occurs
  # when arguments are passed and a default task is defined, and
  # the first given_args does not match the default task.
  # Thor use "help" by default so we skip that case.
  # Note the call to retrieve_task_name. It's called with
  # given_args.dup since that method calls args.shift. Then lookup
  # the task normally. If the first item in given_args is not
  # a task then use the default task. The given_args will be
  # intact later since dup was used.
  if config[:invoked_via_subcommand] && given_args.size >= 1 && default_task != "help" && given_args.first != default_task
    meth ||= retrieve_task_name(given_args.dup)
    task = all_tasks[normalize_task_name(meth)]
    task ||= all_tasks[normalize_task_name(default_task)]
  else
    meth ||= retrieve_task_name(given_args)
    task = all_tasks[normalize_task_name(meth)]
  end
  if task
    args, opts = Thor::Options.split(given_args)
    if stop_on_unknown_option?(task) && !args.empty?
      # given_args starts with a non-option, so we treat everything as
      # ordinary arguments
      args.concat opts
      opts.clear
    end
  else
    args, opts = given_args, nil
    task = Thor::DynamicTask.new(meth)
  end
  opts = given_opts || opts || []
  config.merge!(:current_task => task, :task_options => task.options)
  instance = new(args, opts, config)
  yield instance if block_given?
  args = instance.args
  trailing = args[Range.new(arguments.size, -1)]
  instance.invoke_task(task, trailing || [])
end