module Thor::Base::ClassMethods

def class_options_help(shell, ungrouped_name=nil, extra_group=nil) #:nodoc:

:nodoc:

requires two options: the group name and the array of options.
The second is by returning a lambda used to print values. The lambda

extra_group that should be a hash in the format :group => Array[Options].
hooks to add extra options, one of them if the third argument called
any group, it uses the ungrouped name value. This method provide to
Prints the class options per group. If an option does not belong to 
def class_options_help(shell, ungrouped_name=nil, extra_group=nil) #:nodoc:
  groups = {}
  class_options.each do |_, value|
    groups[value.group] ||= []
    groups[value.group] << value
  end
  printer = proc do |group_name, options|
    list = []
    padding = options.collect{ |o| o.aliases.size  }.max.to_i * 4
    options.each do |option|
      item = [ option.usage(padding) ]
      item.push(option.description ? "# #{option.description}" : "")
      list << item
      list << [ "", "# Default: #{option.default}" ] if option.show_default?
    end
    unless list.empty?
      shell.say(group_name ? "#{group_name} options:" : "Options:")
      shell.print_table(list, :ident => 2)
      shell.say ""
    end
  end
  # Deal with default group
  global_options = groups.delete(nil) || []
  printer.call(ungrouped_name, global_options) if global_options
  # Print all others
  groups = extra_group.merge(groups) if extra_group
  groups.each(&printer)
  printer
end