where I can add a patch to acts_as_tree plugin?
I'm not positive, but I think you'd fork the repo here:
http://github.com/rails/acts_as_tree/tree/master
...make a patch according to the basic idea behind these guidelines:
http://rails.lighthouseapp.com/projects/8994/sending-patches
...and create a ticket with your patch here:
http://rails.lighthouseapp.com/projects/8995-rails-plugins
- Trevor