The largest Git repo on the planet

Over the past 3 months, we have largely completed the rollout of Git/GVFS to the Windows team at Microsoft.As a refresher, the Windows code base is approximately 3.5M files and, when checked in to a Git repo, results in a repo of about 300GB. Further, the Windows team is about 4,000 engineers and the engineering system produces 1,760 daily "lab builds" across 440 branches in addition to thousands of pull request validation builds. All 3 of the dimensions (file count, repo size and activity), independently, provide daunting scaling challenges and taken together they make it unbelievably challenging to create a great experience. Before the move to Git, in Source Depot, it was spread across 40+ depots and we had a tool to manage operations that spanned them.As of my writing 3 months ago, we had all the code in one Git repo, a few hundred engineers using it and a small fraction (