title: How to use environment variables in init container args in kubernetes/openshift?
body: <p>This is an excerpt of my deployment config:</p>
  
  <pre><code>...
  spec:
    containers:
      - env:
          - name: GIT_USERNAME
            valueFrom:
              secretKeyRef:
                key: username
                name: git
          - name: GIT_PASSWORD
            valueFrom:
              secretKeyRef:
                key: password
                name: git
    initContainers:
      - args:
          - clone
          - '--single-branch'
          - '--'
          - 'https://$(GIT_USERNAME):$(GIT_PASSWORD)@someurl.com/something.git'
          - '/testing/'
        image: alpine/git
        imagePullPolicy: Always
        name: init-clone-repo
        resources: {}
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
        volumeMounts:
          - mountPath: /testing
            name: test-volume
    volumes:
      - emptyDir: {}
        name: test-volume
    ...
  </code></pre>
  
  <p>The initContainer fails, because <em>$(GIT_USERNAME)</em> and <em>$(GIT_PASSWORD)</em> are used as is and not expanded. I have tried <em>$GIT_USERNAME</em>, <em>${GIT_USERNAME}</em> and I am pretty much out of ideas.</p>
  
  <p>How do I correctly use environment variables in args for init containers?</p>