Durability on item stacks don't work as expected

When a stack of more than one item loses durability the damage resets and the count is decreased by one. this works as expected, but can be exploited for more durability

Steps to Reproduce:

  1. give yourself 2 of an item that can stack and be damaged, like this one

/give @s minecraft:diamond_pickaxe[max_damage=10, max_stack_size=2] 2

  2. use the item until the stack fully depletes.

      in this example, you should mine 20 blocks.

  3. give yourself the same items but in 2 different stacks.

  4. use each item 9 times.

  5. combine the stacks and continue mining until the stack fully depletes.

      you should have mined 29 blocks.

Observed Results:

  combining the items into one stack can "repair" them, allowing more blocks to be mined.

Expected Results:

  the number of uses should remain the same.