It bothers me that they repeatedly write about a migration "from Mercurial to GitHub", rather than "from Mercurial to Git". It seems to imply that GitHub hosting is the only way to run Git.
It's perfectly fine to say that they are moving to GitHub hosting, but not to put it on the same level as Mercurial: Mercurial and Git are applications/protocols, while GitHub is a hosting service. You should compare application with application and hosting service with hosting service.
Good point, people have largely forgotten the distinction between Git and GitHub.
Recently, I was searching for a Git - fork project (i.e. a project forked from git itself) which allowed separate machine based accounts for Git branches. It was quite famous, I had used it about 4 years back and I don't remember its name now.
Now, this is the worst case scenario for the search engines -
• 'git fork project' would bring numerous github forked projects.
• 'git original source' would bring the mirror of git in github, but then again there are hundreds of fork.
After, lot of time spent on this in vain, I gave up.
UPDATE: While writing this comment I remembered the USP of that project was 'Branch specific permissions', so I gave a fresh attempt at finding it and I did via SO! It's Gitolite[1].