User blog comment:ISharkyShark/Update 1.1/@comment-25014034-20170109053901/@comment-30139169-20170109234457

You may or may not know what Luck does, so I will tell you just in case. And Potion of Luck increases the percentage of getting fish, or getting loot in chests.

EDIT: Never mind, I looked up Potion of Luck, and it said it can't be brewed. Maybe in 1.12 they will add clovers to minecraft.