excerpt drop should give access to document's layout

lib/jekyll/drops/excerpt_drop.rb

@@ -3,6 +3,10 @@
 module Jekyll
   module Drops
     class ExcerptDrop < DocumentDrop
+      def layout
+        @obj.doc.data['layout']
+      end
+
       def excerpt
         nil
       end

test/test_excerpt_drop.rb

@@ -5,7 +5,7 @@ class TestExcerptDrop < JekyllUnitTest
     setup do
       @site = fixture_site
       @site.read
-      @doc = @site.docs_to_write.first
+      @doc = @site.docs_to_write.find { |d| !d.data['layout'].nil? }
       @doc_drop = @doc.to_liquid
       @excerpt = @doc.data['excerpt']
       @excerpt_drop = @excerpt.to_liquid
@@ -24,8 +24,13 @@ class TestExcerptDrop < JekyllUnitTest
       assert_nil @excerpt_drop['excerpt']
     end
 
+    should "inherit the layout for the drop but not the excerpt" do
+      assert_nil @excerpt.data['layout']
+      assert_equal @excerpt_drop['layout'], @doc_drop['layout']
+    end
+
     should "inherit values from the document" do
-      assert_equal @excerpt_drop.keys, @doc_drop.keys
+      assert_equal @excerpt_drop.keys.sort, @doc_drop.keys.sort
     end
   end
 end