title: Use sub directory with kubernetes gitRepo volume mounts
body: <p>Following snippet is from kubernetes official documentation (<a href="http://kubernetes.io/docs/user-guide/volumes/#gitrepo" rel="nofollow">http://kubernetes.io/docs/user-guide/volumes/#gitrepo</a>):</p>
  
  <pre><code>apiVersion: v1
  kind: Pod
  metadata:
    name: server
  spec:
    containers:
    - image: nginx
      name: nginx
      volumeMounts:
      - mountPath: /mypath
        name: git-volume
    volumes:
    - name: git-volume
      gitRepo:
        repository: "git@somewhere:me/my-git-repository.git"
        revision: "22f1d8406d464b0c0874075539c1f2e96c253775"
  </code></pre>
  
  <p>The above will mount complete git repo inside the container at /mypath. Is there a way to mount only specific sub-directory inside of the git repo inside the container at /mypath?</p>