I have a skeleton farm and I enchanted DOZENS of items already. I never saw “mending” though. The Wiki says, that you find this on the lower enchanting levels, but I never saw it.
Note: (Normally) Before I enchant an item, I look through all of them and check on each what I would get: Helmet, Chestplate, Leggings, Boots, Sword, Bow. I think chances that I really never could have seen it are pretty low.
Can you get this enchantment only from the end and from books? I saw some enchanted items in the end cities with mending.
Mending is a treasure enchantment, which you can only find in the world, you can not create it yourself on an enchanting table.
Treasure enchantments can be obtained by
- Chests in dungeons, temples, mineshafts, End cities etc.
- Trading (villagers charge double price for treasure enchantments)
Mending can be found on many items, including, for example, Fishing Rods.