[Someone]

That’s quite a few assumptions, at least one of which likely isn’t correct; at Microsoft, the .git directory doesn’t contain ”all the git files, including file versions […] and branche”

https://devblogs.microsoft.com/devops/optimizing-git-beyond-...:

”GVFS allows our developers to simply not download most of those 3.5 million files during a clone, and instead simply page in the (comparatively) small portion of the source tree that a developer is working with.”

Having said that, the linked https://docs.microsoft.com/en-us/azure/devops/learn/git/gvfs... claims Windows gives a size about half that 500GB for the Windows source code:

”the Windows repo, which has over 3 million files in the working directory, totalling 270GB of source files. That’s 270GB in the working directory, at the tip of master. To clone this repo, you would have to download a packfile that is about 100GB in size, which would take hours. And once you’ve succeeded in cloning it, local git operations like checkout (3 hours), status (8 minutes), and commit (30 minutes) would still take way too long to run”.