WHY FACEBOOK DOESN'T USE GIT

Summary from the TLDR newsletter

Facebook uses Mercurial instead of Git, building custom workflows on top of the tool for performance. Facebook used Git years ago, but it started facing performance issues, and the response from Git maintainers wasn't cooperative, with the maintainers pushing back on improving performance and instead recommending that Facebook shard its monorepo. The Facebook team looked at its alternatives and chose Mercurial, which had a community of maintainers who were welcoming to changes made by them. The story shows how kindness and openness can go far in the world of devtools.