This is so awesome. Brilliant move MS! In addition to enabling Windows engineers to be significantly more productive (eventually), it will go a long way to enabling engineers in other departments to contribute to Windows. For example, I used to work in the Azure org and once noticed a relatively simple missing feature in Windows. I filed a bug and was in contact with a PM who suggested if I wanted I could work on adding it myself. I dipped my toe in, but the onboarding costs were just too high and I quickly decided against it. With Windows on git, much more likely to have dived in.