Windows Source Code Is Live On Git

Microsoft today announced that its Windows operating system source code is now in Git. Windows engineer and developer teams can now use Git repository to build operating systems. The news was announced via a blog post by Brian Harry.

The Windows Git repo has about 3.5M files and 300GB size. About 4,000 engineers of Windows team produce about 1,760 daily “lab builds” across 440 branches in addition to thousands of pull request validation builds.

“Much to my surprise, quite honestly, it went very smoothly and engineers were productive from day one. We had some issues, no doubt. For instance, Windows, because of the size of the team and the nature of the work, often has VERY large merges across branches (10,000’s of changes with 1,000’s of conflicts). We discovered that first week that our UI for pull requests and merge conflict resolution simply didn’t scale to changes that large. We had to scramble to virtualize lists and incrementally fetch data so the UI didn’t just hang. We had it resolved within a couple of days and overall, sentiment that week was much better than we expected.” writes Brian.

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The scale the system is operating at is really amazing. Let’s look at some numbers…

  • There are over 250,000 reachable Git commits in the history for this repo, over the past 4 months.
  • 8,421 pushes per day (on average)
  • 2,500 pull requests, with 6,600 reviewers per work day (on average)
  • 4,352 active topic branches
  • 1,760 official builds per day