Drupal.org apparently doesn't give information for Drupal 8, in the Version control tab of projects. I checked for a project with a Drupal 8 version (the Token module), but even selecting a Drupal 8 branch, the information given is for Drupal 7.
That said, there isn't much difference, with Drupal 8. What I report here are the adapted instructions for Drupal 8.
See the naming conventions for a complete description of how to name branches and tags so you can create releases.
Branch for a dev release
This creates and checks out a new branch in one command, then pushes it to Drupal.org.
git checkout -b 8.x-1.x
git push -u origin 8.x-1.x
Tag for a stable release
git checkout 8.x-1.x
git tag 8.x-1.0
git push origin tag 8.x-1.0