How can we set the ECS Cluster name in YAML override

[WillGibson]

This looks legit to me in copilot/environments/overrides/cfn.patches.yml...

# Set ECS Cluster name so that we can reference it in Terraform without using an external data source
- op: replace
  path: /Resources/Cluster/Properties/ClusterName
  value: !Sub '${AppName}-${EnvName}'

copilot svc deploy does nothing with it though and copilot env deploy says...

deploy environment tf-will: generate template: override template: unable to apply the "replace" patch at index 0: key "/Resources/Cluster/Properties": "ClusterName" not found in map

ClusterName looks like the right thing in the docs.

What am I missing here?

[WillGibson]

I needed to use add not replace, because AWS Copilot does not set the ClusterName, so it cannot be replaced.