Extends keyword

[Zefyro]

Inheriting properties from an already defined file using extends keyword

In simple terms, allow modifying values of a file created using the new keyword without copying the whole file.
This would be really useful for custom advancements that are different by a single line or the likes.

new advancement(blue_reward) {
  "display": {
    "icon": {
      "item": "minecraft:blue_concrete"
    },
    "title": "Example",
    "description": "example",
    "frame": "goal"
  },
  "criteria": {
    "requirement": {
      "trigger": "minecraft:tick",
      "conditions": {
        "player": {
          "team": "blue"
        }
      }
    }
  },
  "rewards": {
    "function": "example:reward"
  }
}

new advancement(red_reward) extends(blue_reward) {
  "display": {
    "icon": {
      "item": "minecraft:red_concrete"
    },
  },
  "criteria": {
    "requirement": {
      "conditions": {
        "player": {
          "team": "red"
        }
      }
    }
  }
}

This would allow one to copy and modify files that require minor changes without completely copying the contents of the file.
This also allows making the same changes to the files faster for example if the reward were changed to also include experience, all the files extending the parent would get the change.

[Nico314159]

+1, this would be a very useful feature

(Definitely would be a relief for all my loot table stuff)