Support relative references taking the current resolution scope into account

[epoberezkin]

See ajv-validator/ajv#278

This should work:

{
  id: 'schema.json#',
  definitions: {
    foo: {
      properties: {
        str: { type: 'string' }
      }
    }
  },
  $merge: {
    source: { $ref: '#/definitions/foo' },
    with: {
      properties: {
        int: { type: 'integer' }
      }
    }
  }
}

At the moment it needs source: { $ref: 'schema.json#/definitions/foo' } in order to work.

[epoberezkin]

That would require adding baseId parameter to custom keyword functions in Ajv, see ajv-validator/ajv#280