Move Filters#sort_input to use a Schwartzian transform.

lib/jekyll/filters.rb

@@ -335,19 +335,23 @@ def inspect(input)
     end
 
     private
+
+    # Sort the input Enumerable by the given property.
+    # If the property doesn't exist, return the sort order respective of
+    # which item doesn't have the property.
+    # We also utilize the Schwartzian transform to make this more efficient.
     def sort_input(input, property, order)
-      input.sort do |apple, orange|
-        apple_property = item_property(apple, property)
-        orange_property = item_property(orange, property)
-
-        if !apple_property.nil? && orange_property.nil?
-          - order
-        elsif apple_property.nil? && !orange_property.nil?
-          + order
-        else
-          apple_property <=> orange_property
+      input.map { |item| [item_property(item, property), item] }
+        .sort do |apple_property, orange_property|
+          if !apple_property.nil? && orange_property.nil?
+            - order
+          elsif apple_property.nil? && !orange_property.nil?
+            + order
+          else
+            apple_property <=> orange_property
+          end
         end
-      end
+        .map(&:last)
     end
 
     private