Everlasting anvil!

[infomercial announcer voice]: Are you tired of anvils always breaking on you? Wish your anvil would last forever just like a real blacksmith's? Well look no further! Through command blocks your anvil will instantly repair itself just seconds after the first crack appears!

Please note: if this does not work for you, open the command block that should be right underneath the anvil, and replace the 6 with a 1, 3, or 10 (Depends which way you place the anvil)

Made & tested on minecraft 1.9.4. (Singleplayer AND Multiplayer (Even bukkit!) compatible)
If you find other version compatibilities, please let me know!