Open Rails migrations in an editor automatically after creation

migration_generator.rb

# As soon as I create a Rails migration I always want to open that file in an editor. 
# I'd like to submit the following patch to Rails to create an --editor argument
# for the migration generator but I can't quite figure out the Thor way of doing this.

require 'rails/generators/active_record'

module ActiveRecord
  module Generators
    class MigrationGenerator < Base
      argument :editor, :type => :string, :lazy_default => ENV['EDITOR'], :required => false, :banner => "/path/to/your/editor", :desc => "Open migration using specified editor (defaults to EDITOR)"
      argument :attributes, :type => :array, :default => [], :banner => "field:type field:type"

      def create_migration_file
        set_local_assigns!
        path = migration_template "migration.rb", "db/migrate/#{file_name}.rb"
        # here's the part where I'd like to use the cmdline argument 
        # instead of EDITOR
        run("#{ENV['EDITOR']} #{path}") 
      end

      protected
        attr_reader :migration_action

        def set_local_assigns!
          if file_name =~ /^(add|remove)_.*_(?:to|from)_(.*)/
            @migration_action = $1
            @table_name       = $2.pluralize
          end
        end

    end
  end
end