added index and existing records update to migration

lib/generators/zodiac/migration/migration_generator.rb

@@ -28,6 +28,10 @@ def migration_classname
       "Add#{sign_attribute.camelcase}To#{model_name.gsub('::', '').camelcase.pluralize}"
     end
 
+    def model_classname
+      model_name.camelcase.singularize
+    end
+
     def table_name
       model_name.underscore.gsub('/', '_').pluralize
     end

lib/generators/zodiac/migration/templates/migration30.rb.erb

@@ -1,9 +1,17 @@
+<%# migration for ActiveRecord 3.0 -%>
 class <%= migration_classname %> < ActiveRecord::Migration
   def self.up
     add_column :<%= table_name %>, :<%= sign_attribute.underscore %>, :integer
+    add_index  :<%= table_name %>, :<%= sign_attribute.underscore %>
+
+    <%= model_classname %>.all.each do |<%= model_name.underscore.singularize %>|
+      <%= model_name.underscore.singularize %>.send(:update_sign_id)
+      <%= model_name.underscore.singularize %>.save
+    end
   end
 
   def self.down
+    remove_index  :<%= table_name %>, :<%= sign_attribute.underscore %>
     remove_column :<%= table_name %>, :<%= sign_attribute.underscore %>
   end
 end

lib/generators/zodiac/migration/templates/migration31.rb.erb

@@ -1,5 +1,12 @@
+<%# migration for ActiveRecord 3.1 and higher -%>
 class <%= migration_classname %> < ActiveRecord::Migration
   def change
     add_column :<%= table_name %>, :<%= sign_attribute.underscore %>, :integer
+    add_index  :<%= table_name %>, :<%= sign_attribute.underscore %>
+
+    <%= model_classname %>.all.each do |<%= model_name.underscore.singularize %>|
+      <%= model_name.underscore.singularize %>.send(:update_sign_id)
+      <%= model_name.underscore.singularize %>.save
+    end
   end
 end