Are you referring to the new UI behavior (new at least to me, since this is the first time I've seen this) when you click on directories/files in the repository file browser like in https://github.com/git/git for example?

I don't really use the github file browser frequently enough to be able to tell if the async loading of the files/directories is what you're referring to. Plus, linking to the github home page was kind of confusing.