Merge instead of overwriting

[minois]

If it gets merged instead of overwriting it will be more convenient.

sample

# sample.yml
・・・
  front:
    <<: !include common.yml
    env:
      CLIENT_MAX_BODY_SIZE: 12M
・・・

# common.yml 
・・・
env:
  LISTEN_UNIX: /tmp/unicorn/unicorn.sock
・・・

before

   "env"=>{"CLIENT_MAX_BODY_SIZE"=>"12M"}},

after

   "env"=>{"LISTEN_UNIX"=>"/tmp/unicorn/unicorn.sock", "CLIENT_MAX_BODY_SIZE"=>"12M"}},

[eagletmt]

This change is too big incompatibility to accept.
What do you think of adding new tag like !merge ?

[minois]

I see, I understood.
It seems good to make a new tag.

[eagletmt]

Hako now supports Jsonnet format #38 .
Merging mappings can be expressed easily by +: syntax sugar.
http://jsonnet.org/docs/tutorial.html