D8 -> D8 node migration I assumed that, since migrate is now in core, migrating nodes from a Drupal 8 site to another Drupal 8 site would be baked in. However, it seems not so.

I have already exported all the node configuration: fields, storage, etc. How can I get the actual node content from a Drupal 8 site to another Drupal 8 site?
As of Jan 11, 2017, there are still no Drupal 8 sources available, per Berdir, Mike Ryan, and others.

To follow along at home, see this issue: https://www.drupal.org/node/2607524