I think people on HN complain way too much about Github's design. Sure you can nitpick this stuff, but Github has always had above-average design. Your comment about design-by-programmer is not really warranted in the context of the monstrosities that the term originally applied to. If you want to hold Github to a higher standard because they have such a great product then fine, but there's no need to be so disparaging.
Github's design is not and has never been terrible. And furthermore, hiring a "real designer" will not solve the problem because the core issue is that Github is a complex product; throwing a designer in there who doesn't understand the nuances of how git is used in the wild is not going to help. There are many different audiences and many different conflicting problems to be solved. The reason there's so much meta information stacked at the top is because the meta information is more commonly used then the file contents in most cases. I agree it's not the most intuitive, but on the other hand there's not an obviously primary role for this page and things are reasonably well organized and delineated based on purpose. I've used almost every single link there and there's not much that doesn't deserve to be front and center.
As for the icon redesign, they are trying to establish a visual language so that the masses of information they are publishing are more readily digestible. This is not something that happens overnight, instead you have to use the icons for a while before they sink and start to pay dividends. I'm not saying Github is successful, but I think people on HN and indeed the Internet in general are way to quick to criticize redesigns based on first impressions.