ConfigMapPropagation controller uses the tracker for a known GVK

[grantr]

Describe the bug
The ConfigMapPropagation controller uses the tracker to watch notifications for a constant GVK (ConfigMap).

Expected behavior
The tracker is only used to watch dynamic GVKs that are unknown at runtime. Informer event handlers expressed in the controller's constructor are clearer indicators (to me) of what watch events will trigger a reconcile.

To Reproduce

Knative release version
HEAD

Additional context
If there's wide agreement about the intended use of the tracker, it might be worth auditing other controllers.

/cc @grac3gao

[grac3gao-zz]

It seems trackers are also used for some known GVK when the association between this tracked resource and the reconciler's master resource is loose.
In Knative Duck Typing, it introduced tracker by the following:

Informers are great when you have something like an OwnerReference to key off of for the association (e.g. impl.EnqueueControllerOf), however, when the association is looser e.g. corev1.ObjectReference, then we need a way of configuring a reconciliation trigger for the cross-reference.

In ConfigMapPropagation (cmp) controller, there are two types of configmap needed to track. One is in the original namespace (which doesn't have OwnerReference with current cmp, and cannot tracked without tracker ), the other one is in current namespace, having OwnerReference.
Thus, I'll just leave the configmap to use tracker in order to make the first case work.

[grantr]

Sounds good, thanks for investigating @grac3gao!

/close

[knative-prow-robot]

@grantr: Closing this issue.

Details

In response to this:

Sounds good, thanks for investigating @grac3gao!

/close

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