Most of monorepo tools for Mercurial are upstreamed already and are available in a standard Mercurial install. I don't think anyone in this thread is CTO of a

Most of monorepo tools for Mercurial are upstreamed already and are available in a standard Mercurial install. I don't think anyone in this thread is CTO of a company size of Facebook. For a medium size company, you can easily use Mercurial or Perforce.