Using the new inventory double click stack in a crafting table, duplicates the item that you are crafting.

I was messing around with the new snapshot 13w01a, and I wanted to try the new crafting mechanics. I was making some diamond blocks and turning them back to diamonds.

Then I realized I left that my inventory was really messy with all the diamonds, so before crafting the diamond blocks back to diamonds, I double clicked them to organize my inventory, but then I noticed that I had more diamonds than before, and I had the same number of diamond blocks.

Steps to Reproduce:
1. Craft an item.
2. Leave it in your inventory.
3. Make the crafting recipe in the crafting table.
4. Double click the same item in your inventory