add optional appcast stanza to DSL

lib/cask/dsl.rb

@@ -10,6 +10,8 @@ def homepage; self.class.homepage; end
 
   def url; self.class.url; end
 
+  def appcast; self.class.appcast; end
+
   def version; self.class.version; end
 
   def depends_on_formula; self.class.depends_on_formula; end
@@ -37,6 +39,15 @@ def url(*args)
       end
     end
 
+    def appcast(*args)
+      if @appcast and !args.empty?
+        raise CaskInvalidError.new(self.title, "'appcast' stanza may only appear once")
+      end
+      @appcast ||= begin
+        Cask::UnderscoreSupportingURI.parse(*args) unless args.empty?
+      end
+    end
+
     def version(version=nil)
       if @version and !version.nil?
         raise CaskInvalidError.new(self.title, "'version' stanza may only appear once")

lib/cask/utils.rb

@@ -51,7 +51,16 @@ def odumpcask cask
   if Cask.respond_to?(:debug) and Cask.debug
     odebug "Cask instance dumps in YAML:"
     odebug "Cask instance toplevel:", cask.to_yaml
-    [:homepage, :url, :version, :sums, :artifacts, :caveats, :depends_on_formula].each do |method|
+    [
+     :homepage,
+     :url,
+     :appcast,
+     :version,
+     :sums,
+     :artifacts,
+     :caveats,
+     :depends_on_formula,
+    ].each do |method|
       odebug "Cask instance method '#{method}':", cask.send(method).to_yaml
     end
   end