`stacker service add` rewrites stacker.yml destructively — strips existing config

[vsilent]

Description

stacker service add redis rewrites the entire stacker.yml file, injecting null structural fields and collapsing existing config_contract details.

Affected Projects

ArchiveBox (likely all projects with config_contract)

Steps to Reproduce

1. Start with a valid stacker.yml with populated config_contract
2. Run stacker service add redis
3. Compare original stacker.yml with the rewritten version

Expected Behavior

Append the requested service while preserving existing config structure and values.

Actual Behavior

• Injects null fields: organization: null, app.dockerfile: null, etc.
• Collapses config_contract.services.app to {}
• Removes explicit ADMIN_PASSWORD contract detail
• File becomes invalid until stacker config fix is run

Example Diff

# Before
config_contract:
  services:
    app:
      environment:
        - name: ADMIN_PASSWORD
          required: true
          secret: true

# After (broken)
config_contract:
  services:
    app: {}

Environment

• Stacker CLI version: latest