This is no good. I respect the UX of this feature, however I don't want new users to learn their git conventions in a browser, this way. I am not sure what GitHub's plan is for taking over the world.. but it would great for new users, if for each of their in-browser actions they provided help text that showed the corresponding CLI command. This reinforces their intent of these kinds of features.
EDIT: That is humorous.. I write the above only to see this: http://try.github.com/. It does not invalidate my argument, but it reinforces GitHub's motivation.