YAML anchor support

[bluepeter]

You can radically reduce your templates down even further using YAML anchors. If you try to use these in the primary CF file, you will get a validation error: "An error occurred (ValidationError) when calling the CreateChangeSet operation: Template error: YAML aliases are not allowed in CloudFormation templates."

However, if you Fn::Include these files from the deployable primary CF files, you can use anchors to cut CF definitions at least in half. E.g., here is an API Gateway endpoint in my YAML:

  /forgot:
  ¦ put:
  ¦ ¦ <<: *scaffold
  ¦ ¦ x-amazon-apigateway-integration:
  ¦ ¦ ¦ <<: *functionCode
  ¦ ¦ ¦ url:
  ¦ ¦ ¦ ¦ Fn::Sub: arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/arn:aws:lambda:${AWS::Region}:${AWS::AccountId}:function:blah/invocations
  ¦ options: *options