For information on setting up a development environment with git to make or test patches, see the Setting up a dev environment document. We work off of the git 8.x branch. The Drupal project page, version control tab has the command to do a git clone of 8.x. If you have trouble getting Drupal 8 installed, or getting tests to pass locally for Drupal 8 head, see issues tagged d8 dev environment and open issues with that tag for any trouble getting set up.
We're currently working our way toward "when it's done" by attacking critical bugs and tasks. Here's how that's going:
More information on the Drupal 8 schedule.
You can read more about the Official Initiatives that added many awesome features to Drupal 8.
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