docs: api: add note about websocket attach streams
Slightly make the change in API v1.42 more visible, and add a snippet
about what users should do to preserve the pre-v1.41 behavior.
@@ -87,8 +87,13 @@ keywords: "API, Docker, rcli, REST, documentation"
* The `Volume` type, as returned by `Added new `ClusterVolume` fields
* Added a new `PUT /volumes{name}` endpoint to update cluster volumes (CNI).
Cluster volumes are only supported if the daemon is a Swarm manager.
-* `/containers/{name}/attach/ws` endpoint only attach to configured streams
- according to `stdin`, `stdout` and `stderr` parameters.
+* `GET /containers/{name}/attach/ws` endpoint now accepts `stdin`, `stdout` and
+ `stderr` query parameters to only attach to configured streams.
+
+ NOTE: These parameters were documented before in older API versions, but not
+ actually supported. API versions before v1.42 continue to ignore these parameters
+ and default to attaching to all streams. To preserve the pre-v1.42 behavior,
+ set all three query parameters (`?stdin=1,stdout=1,stderr=1`).
## v1.41 API changes
