Earlier quoted context omitted.
Microsoft had multiple Github Enterprise accounts before the acquisition, owned by multiple teams independently inside of Microsoft. They chose to use these instead of Microsoft's own internal repository (some VSS-based thing I think), which management ordered them to use. More internal Microsoft code was being hosted by Github instead by Microsoft. However, the Microsoft account on Github seems to only be public rep…
Ah source code at MS. Always amusing to me. VSS [1] (Visual Source Safe) was terrible and I always wondered how "real" companies could use it. From what I heard, MS never did use it, they bought it and sold licenses. That's it. That being said, Microsoft actually moved Windows to Git [2] years and years ago. Presumably they did the same with everything else. Team Foundation Server (TFS) supports Git, so they probably…
Github ended up being the final piece they needed after years of effort. Most of what I said in the earlier comment was what I pieced together from multiple (ex-)Microsoft people who chose to talk about it, over years.
TFS afiact started as just a repo manager (in the sense, does what Github does) for VSS and Perforce, with more modern support for other things, including Microsoft's gargantuan Git monorepo... but a lot of people at Microsoft still like Github Enterprise better.
I imagine given this, whatever TFS does better, Github Enterprise will learn to do over the next few years. Microsoft is big on eating their own dogfood now, but they don't seem to want to do Google sillyness where they have 20 products that do the same thing and let them fight it out in FFA arena combat (even Lync is still Lync underneath, it just keeps getting new frontends).