Support completion for kubectl cp

[superbrothers]

What this PR does / why we need it: With this PR, kubectl cp supports completion. I tested this PR in bash and zsh.

$ kubectl cp kube-system/<tab>
kube-system/kube-state-metrics-769566fdfb-4v52s:   kube-system/kubernetes-dashboard-6b6ddbd46-t5bv9:  kube-system/prometheus-694594c45b-qk5lq:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes kubernetes/kubectl#5

Special notes for your reviewer: @cblecker

Release note:

`kubectl cp` supports completion.

[cblecker]

/ok-to-test

[cblecker]

This looks fine to me.
/lgtm
/assign @deads2k
/test pull-kubernetes-typecheck

[deads2k]

@eparis this sort of thing smells like you. You done completions before? I don't really know what it does.

[soltysh]

/assign @juanvallejo

[juanvallejo]

lgtm. From what I understand, you'll need to specify a namespace foo/ before being able to tab-complete a pod's name right?

[superbrothers]

@juanvallejo No. This completion completes filedirs, <namespace>/, and <pod-name>: of current namespace.

$ kubectl get po
NAME                   READY     STATUS    RESTARTS   AGE
nginx-8586cf59-8qxtc   1/1       Running   0          12s
nginx-8586cf59-scp9r   1/1       Running   0          41s
nginx-8586cf59-w6rnv   1/1       Running   0          12s
$ kubectl cp <tab><tab>
api/                           .dockerized-kube-version-defs  nginx-8586cf59-8qxtc:
.bazelrc                       docs/                          nginx-8586cf59-scp9r:
build/                         examples/                      nginx-8586cf59-w6rnv:
BUILD.bazel                    .generated_files               _output/
CHANGELOG-1.10.md              .git/                          OWNERS
CHANGELOG-1.2.md               .gitattributes                 OWNERS_ALIASES
CHANGELOG-1.3.md               .github/                       pkg/
CHANGELOG-1.4.md               .gitignore                     plugin/
CHANGELOG-1.5.md               Godeps/                        README.md
CHANGELOG-1.6.md               hack/                          staging/
CHANGELOG-1.7.md               .kazelcfg.json                 SUPPORT.md
CHANGELOG-1.8.md               kube-public/                   test/
CHANGELOG-1.9.md               kube-system/                   third_party/
CHANGELOG.md                   labels.yaml                    _tmp/
cluster/                       LICENSE                        translations/
cmd/                           logo/                          vendor/
code-of-conduct.md             .make/                         WORKSPACE
CONTRIBUTING.md                Makefile
default/                       Makefile.generated_files

[superbrothers]

/test pull-kubernetes-integration

[cblecker]

@deads2k Any other concerns before approval?

[superbrothers]

/test pull-kubernetes-integration
/test pull-kubernetes-e2e-gce

[superbrothers]

ping @deads2k @eparis

[cblecker]

ping @deads2k @eparis

[deads2k]

it looks plausible. I guess I'll trust it does good things. In big clusters, the general approach seems questionable.

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cblecker, deads2k, superbrothers

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• pkg/kubectl/OWNERS [deads2k]

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[k8s-github-robot]

/test all [submit-queue is verifying that this PR is safe to merge]

[k8s-github-robot]

Automatic merge from submit-queue (batch tested with PRs 63526, 60371, 63444). If you want to cherry-pick this change to another branch, please follow the instructions here.

[k8s-ci-robot]

@superbrothers: The following tests failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
pull-kubernetes-integration	8d58e70	link	/test pull-kubernetes-integration
pull-kubernetes-e2e-gce	8d58e70	link	/test pull-kubernetes-e2e-gce

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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