Ask HN: Best practices on autoscaled deployment on AWS?

We've been starting to use AWS more, but we're hitting a bit of a wall on how to handle code deployments, particularly in an autoscaling group that isn't done with Elastic Beanstalk.

The main options I see are to either have a script that periodically runs git pull, or to rebuild our AMIs with every deployment and have that push out into the autoscale group. Neither seems particularly ideal. I think I read somewhere that it's possible to do this with CloudFormation, but I don't see how that could work.

For reference, we do development in PHP, nodejs, and Python, and it seems like each instance would require something a bit specialized. And all of our code is in git repos.

Anyway, any advice would be much appreciated. Articles, walkthroughs, that sort of thing. I'll try to answer any questions that there might be. Thanks!