drops: use def_delegator more liberally where acceptable

lib/jekyll/drops/collection_drop.rb

@@ -6,6 +6,7 @@ module Jekyll
     class CollectionDrop < ImmutableDrop
       extend Forwardable
 
+      def_delegator :@obj, :write?, :output
       def_delegators :@obj, :label, :docs, :files, :directory,
                             :relative_directory
 
@@ -13,14 +14,8 @@ module Jekyll
         docs.to_s
       end
 
-      def output
-        @obj.write?
-      end
-
       private
-      def fallback_data
-        @obj.metadata
-      end
+      def_delegator :@obj, :metadata, :fallback_data
 
     end
   end

lib/jekyll/drops/document_drop.rb

@@ -5,22 +5,15 @@ module Jekyll
     class DocumentDrop < ImmutableDrop
       extend Forwardable
 
+      def_delegator :@obj, :next_doc, :next
+      def_delegator :@obj, :previous_doc, :previous
+      def_delegator :@obj, :relative_path, :path
       def_delegators :@obj, :id, :output, :content, :to_s, :relative_path, :url
 
-      alias_method :path, :relative_path
-
       def collection
         @obj.collection.label
       end
 
-      def next
-        @obj.next_doc
-      end
-
-      def previous
-        @obj.previous_doc
-      end
-
       def excerpt
         fallback_data['excerpt'].to_s
       end

lib/jekyll/drops/site_drop.rb

@@ -30,9 +30,7 @@ module Jekyll
       end
 
       private
-      def fallback_data
-        @obj.config
-      end
+      def_delegator :@obj, :config, :fallback_data
 
     end
   end

lib/jekyll/drops/url_drop.rb

@@ -3,18 +3,15 @@
 module Jekyll
   module Drops
     class UrlDrop < ImmutableDrop
+      extend Forwardable
+
+      def_delegator :@obj, :cleaned_relative_path, :path
+      def_delegator :@obj, :output_ext, :output_ext
+
       def collection
         @obj.collection.label
       end
 
-      def path
-        @obj.cleaned_relative_path
-      end
-
-      def output_ext
-        @obj.output_ext
-      end
-
       def name
         Utils.slugify(@obj.basename_without_ext)
       end