This change is 

Hi @CaoShuFeng. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with @k8s-bot ok to test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

/assign @janetkuo

@k8s-bot ok to test

@janetkuo
For example, "kubectl set subject" only support "rolebinding/clusterrolebinding" but the help message uses "pods my-pod/services" as an example. In fact, we can't use "kubectl set subject pods".

@k8s-bot verify test this

@CaoShuFeng I see, that makes sense. Please put the options validation code in Validate, ref kubectl convention https://github.com/kubernetes/community/blob/master/contributors/devel/kubectl-conventions.md#command-implementation-conventions

@janetkuo
Looks like someone else met a similar problem before:
https://github.com/kubernetes/kubernetes/blob/master/pkg/kubectl/resource/builder.go#L91
So is use this API to check the error.

Please put the options validation code in Validate

I tried your suggestion, but I found that error happens before we call Validate(), so it's difficult to check options in Validate().

@k8s-bot pull-kubernetes-federation-e2e-gce test this

@CaoShuFeng I see, the missingResourceError is returned by resource builder. We can just modify the example part of missingResourceError -- don't use concrete examples since it's a generic error for kubectl, but not all commands support the resources specified in the example.

In summary, change it to something like:

var missingResourceError = fmt.Errorf(`You must provide one or more resources by argument or filename.
Example resource specifications include:
   '-f app.yaml'
   '--filename=app.json'
   '<resource> <name>'
   '<resource>'`)

@janetkuo
Done.

@k8s-bot unit test this

Thanks!
/lgtm
/approve

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CaoShuFeng, janetkuo

@k8s-bot gce etcd3 e2e test this

Automatic merge from submit-queue