With the status of existing plugins, you will need to do some optimization. The site team (for your comments: you want to use mvn: site) has a mechanism (stage) for pushing the resulting site somewhere, but it was all mainly based on SCP'ing around some final destination. For github, I don’t think there is any obvious place to land like that.
The solution would be to write something that expanded the site plugin to test the results on Github using the functionality of the github pages. Details on github page bits are available at http://pages.github.com/ . To get there, you will write something that checks the root branch of "gh-pages" on your resulting site and from there.