Lots of interesting pieces of info in this article, like this:
For example, the Windows codebase has over 3.5 million files and is over 270 GB in size.
But GVFS itself is more interesting:
[…] we’ve been working hard on a solution that allows the Git client to scale to repos of any size. Today, we’re introducing GVFS (Git Virtual File System), which virtualizes the file system beneath your repo and makes it appear as though all the files in your repo are present, but in reality only downloads a file the first time it is opened.
GVFS also actively manages how much of the repo Git has to consider in operations like checkout and status, since any file that has not been hydrated can be safely ignored.