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:
aa81efb0 Remove some additional draft API markings
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.
This allows plugins that give players the ability to apply the experience
points to the Item Mending formula, which will repair an item instead
of giving the player experience points.
Both an API To standalone mend, and apply mending logic to .giveExp has been added.