Broken kubectl completion with override flags

[tatsuhiro-t]

What happened:

With kubectl v1.16.0-alpha.2, completion with override flags fails.
kubectl --kubeconfig=foo -n then hit TAB will produce error "resource type must be specified"

What you expected to happen:

It must show the namespaces without error.

How to reproduce it (as minimally and precisely as possible):

With kubectl v1.16.0-alpha.2, kubectl --kubeconfig=foo -n then hit TAB key.

Anything else we need to know?:

It looks like #70470 introduced this regression.

Environment:

• Kubernetes version (use kubectl version): kubectl v1.16.0-alpha.2
• Cloud provider or hardware configuration:
• OS (e.g: cat /etc/os-release):
• Kernel (e.g. uname -a):
• Install tools:
• Network plugin and version (if this is a network-related bug):
• Others:

[tatsuhiro-t]

/sig cli

[superbrothers]

I also reproduced this bug with the following steps:

$ bash --version
GNU bash, version 4.4.12(1)-release (x86_64-apple-darwin15.6.0)
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ git checkout 978c38d488e6339aa294aa28b084f9c9626f83ab
Previous HEAD position was 79aab0b90d... Merge pull request #78246 from mborsz/kubemark
HEAD is now at 978c38d488... Merge pull request #70470 from dtaniwaki/fix-auto-completion
$ make kubectl
+++ [0731 17:57:47] Building go targets for darwin/amd64:
    cmd/kubectl
$ _output/bin/kubectl version
Client Version: version.Info{Major:"1", Minor:"16+", GitVersion:"v1.16.0-alpha.0.2059+978c38d488e633-dirty", GitCommit:"978c38d488e6339aa294aa28b084f9c9626f83ab", GitTreeState:"dirty", BuildDate:"2019-07-31T08:57:47Z", GoVersion:"go1.12.6", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"14", GitVersion:"v1.14.4", GitCommit:"a87e9a978f65a8303aa9467537aa59c18122cbf9", GitTreeState:"clean", BuildDate:"2019-07-08T08:43:10Z", GoVersion:"go1.12.5", Compiler:"gc", Platform:"linux/amd64"}
$ . "/usr/local/etc/profile.d/bash_completion.sh"
$ source <(_output/bin/kubectl completion bash)
$ kubectl --kubeconfig ./kubeconfig -n You must specify the type of resource to get. Use "kubectl api-resources" for a complete list of supported resources.

error: Required resource not specified.
Use "kubectl explain <resource>" for a detailed description of that resource (e.g. kubectl explain pods).
See 'kubectl get -h' for help and examples

Error: flag needs an argument: 'n' in -n
(...)

[dtaniwaki]

I'm fixing it.