Why did Facebook choose Mercurial over Git?

from a previous blog post:

"Our engineers were comfortable with Git and we preferred to stay with a familiar tool, so we took a long, hard look at improving it to work at scale. After much deliberation, we concluded that Git's internals would be difficult to work with for an ambitious scaling project."

https://code.facebook.com/posts/218678814984400/scaling-merc...

Note that Microsoft arrived at the opposite conclusion and wrote GVFS: https://github.com/Microsoft/GVFS

Reading that it sounds like they reached the same conclusion, that they didn't want to mess with git's internals. They wrote a filesystem to run underneath git.