Added XML::Node#each_ancestor

This method can be used to walk through the ancestor tree of a Node.

lib/oga/xml/node.rb

@@ -214,6 +214,26 @@ module Oga
       def xml?
         !html?
       end
+
+      ##
+      # Yields all ancestor elements of the current node.
+      #
+      # @example
+      #  some_element.each_ancestor do |node|
+      #    # ...
+      #  end
+      #
+      # @yieldparam [Oga::XML::Node]
+      #
+      def each_ancestor
+        node = parent
+
+        while node.is_a?(XML::Element)
+          yield node
+
+          node = node.parent
+        end
+      end
     end # Element
   end # XML
 end # Oga

spec/oga/xml/node_spec.rb

@@ -276,4 +276,18 @@ describe Oga::XML::Node do
       node.xml?.should == false
     end
   end
+
+  describe '#each_ancestor' do
+    before do
+      @child2   = Oga::XML::Element.new(:name => 'c')
+      @child1   = Oga::XML::Element.new(:name => 'b', :children => [@child2])
+      @root     = Oga::XML::Element.new(:name => 'a', :children => [@child1])
+      @document = Oga::XML::Document.new(:children => [@root])
+    end
+
+    it 'yields all the ancestor elements' do
+      expect { |b| @child2.each_ancestor(&b) }
+        .to yield_successive_args(@child1, @root)
+    end
+  end
 end