Implement recipe arguments

CLI will stop arguments processing after the special `--' argument,
the rest will be saved in the env and accessible through a new task
keyword: `recipe_argv'.

features/steps/recipe_steps.rb

@@ -51,6 +51,11 @@ When /^I successfully execute the recipe with option (-.+)$/ do |option|
   assert_exit_status 0
 end
 
+When /^I successfully execute the recipe with arguments "([^"]+)"$/ do |arguments|
+  run_simple "producer recipe.rb -- #{arguments}", false
+  assert_exit_status 0
+end
+
 When /^I execute the recipe interactively$/ do
   run_interactive 'producer recipe.rb'
 end

features/task/recipe_argv.feature

@@ -0,0 +1,13 @@
+Feature: `recipe_argv' task keyword
+
+  Background:
+    Given a recipe with:
+      """
+      task :echo_arguments do
+        echo recipe_argv
+      end
+      """
+
+  Scenario: returns recipe arguments
+    When I successfully execute the recipe with arguments "foo bar"
+    Then the output must contain exactly "foo\nbar\n"