In testing the new repair mechanics, I've had my tools received damage but suddenly be fully repaired upon a second inspection, or when placed into the anvil interface.

To Reproduce:

Get yourself some diamond gear, spare diamonds, levels and an anvil. Press F3+H to view item damage in your tooltip. Whack away at a few blocks until you see damage. Press E and mouse over the item to view it's durability. Head over to your anvil and repair. Rinse and repeat until you see it happen.

I'll be able to damage and repair a tool properly as many as a dozen times, but eventually I'll see the durability bar appear, mouse over and confirm the damaged state, head to my anvil and find the item to be undamaged.