class Middleman::Extension

def bind_after_build
  ext = self
  return unless ext.respond_to?(:after_build)
  @app.after_build do |builder|
    if ext.method(:after_build).arity == 1
      ext.after_build(builder)
    elsif ext.method(:after_build).arity == 2
      ext.after_build(builder, builder.thor)
    else
      ext.after_build
    end
  end
end