oc rsh: properly shadow position of --

[ingvagabund]

As of k8s 1.18, kubectl exec expects the command preceded by '--' as seen from the help:

Usage:
  kubectl exec (POD | TYPE/NAME) [-c CONTAINER] [flags] -- COMMAND [args...] [options]

If '--' is not present, kubectl exec prints the following informative message:

kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl kubectl exec [POD] -- [COMMAND] instead.

The message is still informative though given oc rsh does not require additional '--',
it's confusing.

In more detail 1.18 rebase brings the following lines in kubectl exec code:

if argsLenAtDash > -1 {
	p.Command = argsIn[argsLenAtDash:]
} else if len(argsIn) > 1 {
	fmt.Fprint(p.ErrOut, "kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl kubectl exec [POD] -- [COMMAND] instead.\n")
	p.Command = argsIn[1:]
} else if len(argsIn) > 0 && len(p.FilenameOptions.Filenames) != 0 {
	fmt.Fprint(p.ErrOut, "kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl kubectl exec [POD] -- [COMMAND] instead.\n")
	p.Command = argsIn[0:]
	p.ResourceName = ""
}

From oc rsh help:

$ ./oc rsh --help
Open a remote shell session to a container
 ...
Options:
  -c, --container='': Container name; defaults to first container
  -T, --no-tty=false: Disable pseudo-terminal allocation
      --pod-running-timeout=1m0s: The length of time (like 5s, 2m, or 3h, higher than zero) to wait
until at least one pod is running
      --shell='/bin/sh': Path to the shell command
  -t, --tty=false: Force a pseudo-terminal to be allocated

Use "oc options" for a list of global command-line options (applies to all commands).

there's no --filename option present (as it in kubectl exec), Thus, no need to assume else if len(argsIn) > 0 && len(p.FilenameOptions.Filenames) != 0 branch gets executed. Leaving only else if len(argsIn) > 1 case which, when argsLenAtDash is set to 1, the first if branch is executed and thus skipping the deprecated message.

[soltysh]

/lgtm
/approve

[openshift-ci-robot]

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