Performance is not the reason GitHub chose git over mercurial. They chose git because their core developers understand internal architecture of git better. They were more proficient in Ruby and C than Python, so git was a natural choice for GitHub.
Python language used mercurial for quite sometime to manage all it's repository, they moved to GitHub not for performance but for inertia of mass adoption, knowing very well that git has inferior user interface and they need to rely on GitHub to make it work for them. Facebook, Unity engine still use mercurial.
Python language used mercurial for quite sometime to manage all it's repository, they moved to GitHub not for performance but for inertia of mass adoption, knowing very well that git has inferior user interface and they need to rely on GitHub to make it work for them. Facebook, Unity engine still use mercurial.