I don't know what they use in production, but Matt (mercurial project leader) currently works for FB: http://mercurial.selenic.com/wiki/mpm http://mercurial.sel

I don't know what they use in production, but Matt (mercurial project leader) currently works for FB: http://mercurial.selenic.com/wiki/mpm http://mercurial.selenic.com/wiki/mpm FB hired quite a few mercurial hacker, they host Mercurial sprints and have a big attendance from FB devs (e.g. London sprint): http://mercurial.selenic.com/wiki/2.6sprint http://mercurial.selenic.com/wiki/2.6sprint