ISO week date drops (#5981)

Merge pull request 5981

lib/jekyll/configuration.rb

@@ -305,6 +305,8 @@ module Jekyll
         "/:categories/:year/:month/:day/:title:output_ext"
       when :ordinal
         "/:categories/:year/:y_day/:title:output_ext"
+      when :weekdate
+        "/:categories/:year/W:week/:short_day/:title:output_ext"
       else
         permalink_style.to_s
       end

lib/jekyll/drops/url_drop.rb

@@ -35,46 +35,89 @@ module Jekyll
         category_set.to_a.join("/")
       end
 
+      # CCYY
       def year
         @obj.date.strftime("%Y")
       end
 
+      # MM: 01..12
       def month
         @obj.date.strftime("%m")
       end
 
+      # DD: 01..31
       def day
         @obj.date.strftime("%d")
       end
 
+      # hh: 00..23
       def hour
         @obj.date.strftime("%H")
       end
 
+      # mm: 00..59
       def minute
         @obj.date.strftime("%M")
       end
 
+      # ss: 00..59
       def second
         @obj.date.strftime("%S")
       end
 
+      # D: 1..31
       def i_day
         @obj.date.strftime("%-d")
       end
 
+      # M: 1..12
       def i_month
         @obj.date.strftime("%-m")
       end
 
+      # MMM: Jan..Dec
       def short_month
         @obj.date.strftime("%b")
       end
 
+      # MMMM: January..December
+      def long_month
+        @obj.date.strftime("%B")
+      end
+
+      # YY: 00..99
       def short_year
         @obj.date.strftime("%y")
       end
 
+      # CCYYw, ISO week year
+      # may differ from CCYY for the first days of January and last days of December
+      def w_year
+        @obj.date.strftime("%G")
+      end
+
+      # WW: 01..53
+      # %W and %U do not comply with ISO 8601-1
+      def week
+        @obj.date.strftime("%V")
+      end
+
+      # d: 1..7 (Monday..Sunday)
+      def w_day
+        @obj.date.strftime("%u")
+      end
+
+      # dd: Mon..Sun
+      def short_day
+        @obj.date.strftime("%a")
+      end
+
+      # ddd: Monday..Sunday
+      def long_day
+        @obj.date.strftime("%A")
+      end
+
+      # DDD: 001..366
       def y_day
         @obj.date.strftime("%j")
       end