I am running an application with 2 replicas, and I want to ensure zero downtime when upgrading the Docker image. Specifically, I want Watchtower to update the replicas one by one, so that at least one replica remains running at all times.

The documentation states:
"Restart one image at a time instead of stopping and starting all at once."

However, since my replicas are based on the same image, it's unclear to me whether the --rolling-restart option restarts each replica individually or if it still results in downtime for the entire service. Could you clarify if this option ensures one-by-one rolling updates for replicas?

services:
  webapp:
    image: myapp:latest
    deploy:
      replicas: 2