While Rails has great support for adding Rake tasks there is currently no information on how to add Thor commands, despite Thor playing an active role internally. I find Thor commands to be better for handling more sophisticated interaction from the user and they’re great for testing. There already seems to be solid conventions in place for Rails/Thor commands for either engines or applications however, this is currently undocumented.
I just wrote an article describing how an app or engine author can add their own namespaced Commands here: http://www.joshklina.com/posts/adding-thor-commands-to-rails
I’d be happy to create a patch that adds a Command generator and write up documentation if you folks would be interested.