https://www.youtube.com/watch?v=eohYt3y6ZU8&feature=youtu.be

You can see the exact process in this video

Take a pickaxe into your hands and in survival mode break a block with it, then holding exact same pickaxe run the command below

command: /execute store success entity @s SelectedItem.tag.Damage int 100 if entity @s

In single player and on the vanilla server the damage of the pickaxe changes, but on spigot it doesn't