> GitHub—which was acquired by Microsoft in 2018 The makers of Sharepoint and Sourcesafe bought Github, truly the end of an era. :(
To be fair, the guys who rejected Sharepoint and Sourcesafe (for being shit) to have secret "illegal" Github Enterprise accounts (not managed by Microsoft Corp, but internally by the team) who later became upper management and executives are the ones that bought Github. Microsoft culturally changed, hard; in some ways good, in some ways bad. Fun fact, they had an internal proposal to buy Github when it was much small…
Maybe you're talking about something different, but this happened, didn't it? ADO supports Git alongside TFS (not Sourcesafe, but Sourcesafe has been dead forever and was pretty much dead when GitHub first started). It's very much store-brand GitHub repos, much of it is the same but there's tons of features missing and the code review tools aren't as good.
As far as I know (per publicly released blogs/docs/talks), the Windows monorepo lives inside ADO, not GitHub.