AWS::ECS::TaskDefinitionでリビジョンを含まないARNをエクスポートする

ecs_taskdefinition.yaml

AWSTemplateFormatVersion: '2010-09-09'

Parameters:
  EnvironmentName:
    Type: String
    Default: "MyApp"
# ...

Resources:
  ECSTaskDefinition:
    Type: AWS::ECS::TaskDefinition
# ...

Outputs:
  ECSTaskDefinitionArn:
    Value: 
      Fn::Join:
        - "/"
        - - Fn::Select:
            - 0
            - Fn::Split:
              - "/"
              - !Ref ECSTaskDefinition
          - !Sub "${EnvironmentName}"
    Export:
      Name: !Sub "${EnvironmentName}-ECSTaskDefinitionArn"