alias --help to help on subcommands

When the --help option is present it will change the args array to
include the help command.

Author: developingchris

lib/thor.rb

@@ -229,6 +229,7 @@ def subcommand(subcommand, subcommand_class)
 
       define_method(subcommand) do |*args|
         args, opts = Thor::Arguments.split(args)
+        args.unshift("help") if opts.include? "--help"
         invoke subcommand_class, args, opts, :invoked_via_subcommand => true, :class_options => options
       end
     end
@@ -353,6 +354,7 @@ def dispatch(meth, given_args, given_opts, config) #:nodoc:
         command = Thor::DynamicCommand.new(meth)
       end
 
+
       opts = given_opts || opts || []
       config.merge!(:current_command => command, :command_options => command.options)
 

spec/subcommand_spec.rb

@@ -25,6 +25,13 @@
       output = capture(:stdout) { TestSubcommands::Parent.start(%w[sub print_opt --opt output]) }
       expect(output).to eq("output")
     end
+
+    it "accepts the help switch and calls the help command on the subcommand" do
+      output = capture(:stdout) { TestSubcommands::Parent.start(%w[sub print_opt --help])}
+      sub_help = capture(:stdout) { TestSubcommands::Parent.start(%w[sub help print_opt])}
+      expect(output).to eq(sub_help)
+    end
+
   end
 
 end