This module is a Hoe plugin. You can set its attributes in your Rakefile‘s Hoe spec, like this:

   Hoe.plugin :isolate

   Hoe.spec "myproj" do
     self.isolate_dir = "tmp/isolated"
   end

NOTE! The Isolate plugin is a little bit special: It messes with the plugin ordering to make sure that it comes before everything else.