Meta's Sapling source-code management system

I'd be a bit sceptical of using Facebook stuff outside of FB. There are internal brownie points for releasing stuff as open-source perhaps, but there are few to none for taking the time to maintain open-source stuff. Also, the internal culture is to build everything from a mono-repo, and have no concern for backward compatibilities (other than the non-atomic roll outs of binaries/artifacts from a build from said mono-repo). So I'd hate to depend on FB code outside of FB. In particular, the FB C++ library (folly) maintainers explicitly are hostile to attempts to make life easier for maintaining code out of FBCode that depends on their stuff.