Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
Bukkit Changes:
8ab814cd Add getFacing method to get the current cardinal direction an entity is facing.
CraftBukkit Changes:
ee5efeb0 Add getFacing method to get the current cardinal direction an entity is facing.
Spigot Changes:
0ede7d0e Rebuild patches
This branch/commit is only useful to those who purely use a clean Bukkit/Spigot/Paper API
and does not use NMS/OBC references.
This will let you start updating your plugin to the latest 1.13 builds of Bukkit Preview (4 as of now)
Note that this release is not final!!! API breakages may occur!
It is up to you if you find use out of this work.