Merge pull request #49854 from adriananeci/enhance_revisionHistoryLimit

Add note about deployment cleanup policy

Author: k8s-ci-robot

content/en/docs/concepts/workloads/controllers/deployment.md

@@ -1079,6 +1079,16 @@ Explicitly setting this field to 0, will result in cleaning up all the history o
 thus that Deployment will not be able to roll back.
 {{< /note >}}
 
+The cleanup only starts **after** a Deployment reaches a 
+[complete state](/docs/concepts/workloads/controllers/deployment/#complete-deployment).
+If you set `.spec.revisionHistoryLimit` to 0, any rollout nonetheless triggers creation of a new
+ReplicaSet before Kubernetes removes the old one.
+
+Even with a non-zero revision history limit, you can have more ReplicaSets than the limit
+you configure. For example, if pods are crash looping, and there are multiple rolling updates
+events triggered over time, you might end up with more ReplicaSets than the 
+`.spec.revisionHistoryLimit` because the Deployment never reaches a complete state.
+
 ## Canary Deployment
 
 If you want to roll out releases to a subset of users or servers using the Deployment, you