getContainerByServiceName expects an instance name

#2314 brought support for selecting a container based on the service name when using docker-compose (thanks 🙌 !). However, the value it expects contains the "container number" (e.g. service_1), instead of just the service name, e.g. just service.

This does not match the behaviour of using docker-compose directly:

$ docker-compose ps agent
      Name             Command       State   Ports
--------------------------------------------------
myapp_agent_1   /bin/k3s agent   Up

$ docker-compose ps agent_1
ERROR: No such service: agent_1

According to this test, it looks like the expected behavior, or maybe was incorrectly modeled.

Maybe using getServiceInstanceName from getContainerByServiceName would provide compatibility for both cases?

まず getContainerByServiceName と、pull request #2314 で参照されている test を読み、現在の lookup と docker-compose ps service-name の動作を比較します。lookup が service name を一貫して受け付け、意図された instance-name 互換性を維持したうえで、関連する test が更新または追加されていれば完了です。