https://forum.xda-developers.com/attachment.php?attachmentid=4119155&d=1492674388
This is the restore zip. Follow the guide on the urbane thread but flash the original 2.0 update for the Watch R instead of the Urbane stuff.
The new sources aren't out till now. I made this app https://play.google.com/store/apps/details?id=com.skin1980.buttonremap where you can add any app or custom shell command to the long press.