Expected Behavior

When defining parameters for a Task in my Pipeline, I would like to use values for the parameters which I defined in a ConfigMap, instead of hardcoding them in the Pipeline.

A cool solution would look like the use of ConfigMaps when defining environment variables in a Pod, there I am able to do this:

        env:
        - name: SOME_ENV_VARIABLE
          valueFrom:
            configMapKeyRef:
              name: my-config
              key: my-key

if params could work the same way it would be like this:

          params:
          - name: some-parameter
            valueFrom:
              configMapKeyRef:
                name: pipeline-config
                key: some-key

Actual Behavior

If I want to use a ConfigMap I can only use it on a Step level, and I can't directly access its values, this becomes an issue in the following Task:

apiVersion: tekton.dev/v1alpha1
kind: Task
metadata:
  name: pmd-test
spec:
  inputs:
    resources:
      - name: git-source-code
        type: git
    params:
      - name: image
        type: string
        description: The image that will be used in the test
        default: rawdee/pmd
      - name: command
        type: string
        description: The command that will be used in the test
        default: pmd
      - name: args
        type: string
        description: The args that will be used in the test
        default: -language java -dir /workspace/git-source-code -rulesets ./my-rulesets.xml
  steps:
    - name: test-pmd
      image: $(input.params.image)
      command: ["$(input.params.command)"]
      args: ['$(input.params.args)']

in this example, I want to have the possibility configure the entire Step based on the ConfigMap, but currently it would look like this:

apiVersion: tekton.dev/v1alpha1
kind: Task
metadata:
  name: pmd-test
spec:
  volumes:
    - name: config-volume
      configMap:
        name: pipeline-config
  inputs:
    resources:
      - name: git-source-code
        type: git
  steps:
    - name: test-pmd
      volumeMounts:
        - name: config-volume
          mountPath: /my-path
      image: $(cat /my-path/my-image)
      command: ["$(cat /my-path/my-command)"]
      args: ['$(cat /my-path/my-args)]

Note that this wouldn't work for the image since I'm only able to use variable substitution there.