How Microsoft Office Moved from Source Depot to Git

Summary

After going in deep in product, I found myself drawn to a different challenge: making other developers more productive. As one of my biggest mentors would always say: “Developer productivity is always ‘Multiplier work’, especially in places where you have a lot of developers. By saving a couple minutes from every developer, every day, you’ve saved years of human life waiting for stuff.” The project that really forged me was the Office migration from Source Depot to Git. Source Depot: A Journey to the Past Come kids, gather around. Let me tell you youngsters about the ancient times of source control, back when dinosaurs roamed the Earth and before Git and GitHub were even a twinkle in Linus Torvalds’ eye. In the early 2000s, Microsoft faced a dilemma. Windows was growing enormously complex, with millions of lines of code that needed versioning. Git? Didn’t exist. SVN? Barely crawling out of CVS’s shadow. No, children, these were the dark ages of version control. Perforce was one of the few commercial options available—expensive but powerful for its time. Microsoft, being Microsoft, decided to build their own system based on Perforce technology. And thus, Source Depot was born. Using Source Depot was weird, it felt a little bit like programming with oven mitts on: iterations were faster, but branching and switching state were painful. Also, it didn’t help that a single get of the office repo took some hours. Want to check out code? Type sd get (a.k.a osync) and wait. And wait. And perhaps make yourself a sandwich while waiting. Branching? Oh, my sweet summer children. Creating a branch wasn’t the casual git checkout -b you casually toss around today. It was an event. Something you planned for, scheduled, and possibly created a small ritual around. (And pray you don’t have a name conflict.) Everything was centralized—if the network went down, productivity ceased. If you were working remotely? Well, VPN and prayer were your only options. (And VPN was only to get into th...