The Magento2 dev team is now using Github in the traditional sense: They have an internal repo that gets pushed out to github at the end of their sprint. All commits stay intact. This is WAY better than the previous method of pushing a giant commit with everything each sprint.
It’s not just code that has been opened up. The documentation lives on Github now too.
These are all great changes. The more eyes we have on code the better. Do your part: Install the Magento 2 developer preview and get testing