Manipulate previous values

[Moved to @ad-si]

2015-11-07 16:08:07:
  title: Butter
  tags:
    - groceries
    - food
  object:
    test:
      name: John
      age: 34

# Add elements to array
2015-11-12 13:08:07:
  +tags:
    - &id001 test

# Remove elements from array
2015-11-12 13:34:07:
  -tags:
    - *id001

# Delete keys
2015-11-12 13:45:07:
  object:
    test: