Add --rc description on the command line

railties/lib/rails/generators/app_base.rb

@@ -61,6 +61,9 @@ def self.add_shared_options_for(name)
         class_option :skip_test_unit,     type: :boolean, aliases: '-T', default: false,
                                           desc: 'Skip Test::Unit files'
 
+        class_option :rc,                 type: :string, default: false,
+                                          desc: "Path to file containing extra configuration options for rails command"
+
         class_option :no_rc,              type: :boolean, default: false,
                                           desc: 'Skip loading of extra configuration options from .railsrc file'