Add the ability to describe input filters

lib/mutations/command.rb

@@ -51,6 +51,10 @@ def input_filters
         end
       end
 
+      def input_descriptions
+        input_filters.input_descriptions if input_filters.respond_to?(:input_descriptions)
+      end
+
     end
 
     # Instance methods

lib/mutations/hash_filter.rb

@@ -5,6 +5,10 @@ def self.register_additional_filter(type_class, type_name)
         name = args[0]
         options = args[1] || {}
 
+        if described = current_input_description
+          @input_descriptions[name.to_sym] = described
+        end
+
         @current_inputs[name.to_sym] = type_class.new(options, &block)
       end
     end
@@ -16,10 +20,13 @@ def self.register_additional_filter(type_class, type_name)
     attr_accessor :optional_inputs
     attr_accessor :required_inputs
 
+    attr_accessor :input_descriptions, :input_description
+
     def initialize(opts = {}, &block)
       super(opts)
 
       @optional_inputs = {}
+      @input_descriptions = {}
       @required_inputs = {}
       @current_inputs = @required_inputs
 
@@ -39,6 +46,16 @@ def dup
       dupped
     end
 
+    def desc input_description
+      @input_description = input_description
+    end
+
+    def current_input_description
+      val = @input_description && @input_description.dup
+      @input_description = nil
+      val
+    end
+
     def required(&block)
       @current_inputs = @required_inputs
       instance_eval &block