Implement `has_dir' condition keyword

lib/producer/core/condition/dsl.rb

@@ -14,6 +14,7 @@ module Producer
         end
 
         define_test :has_env,   Tests::HasEnv
+        define_test :has_dir,   Tests::HasDir
         define_test :has_file,  Tests::HasFile
 
         attr_reader :block, :env, :tests

lib/producer/core/tests/has_dir.rb

@@ -0,0 +1,11 @@
+module Producer
+  module Core
+    module Tests
+      class HasDir < Test
+        def verify
+          fs.dir? arguments.first
+        end
+      end
+    end
+  end
+end