Kind: correctly check KUBECONFIG when deleting clusters

[BenTheElder]

This check is incomplete:
https://github.com/kubernetes-sigs/kind/blob/2b270a02556671be069c19c38a404a1eaf5951a9/pkg/cluster/context.go#L382-L385

Per [the official docs], KUBECONFIG may contain multiple paths. The current naive check is insufficient.

NOTE: this only affects wether we give help text or not, so it is not critical. But we should do the correct thing.

/priority backlog
/help

[k8s-ci-robot]

@BenTheElder:
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In response to this:

This check is incomplete:
https://github.com/kubernetes-sigs/kind/blob/2b270a02556671be069c19c38a404a1eaf5951a9/pkg/cluster/context.go#L382-L385

Per [the official docs], KUBECONFIG may contain multiple paths. The current naive check is insufficient.

/priority backlog
/help

[the official docs]: https://kubernetes.io/docs/tasks/access-application-cluster/configure-access-multiple-clusters/#set-the-kubeconfig-environment-variable

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[neolit123]

/assign

[manparvesh]

Hi, can I work on this issue?

[neolit123]

/unassign
sure @manparvesh

[manparvesh]

@neolit123 thanks, I will assign it to myself
/assign

[k8s-ci-robot]

@manparvesh: GitHub didn't allow me to assign the following users: manparvesh.

Note that only kubernetes-sigs members and repo collaborators can be assigned and that issues/PRs can only have 10 assignees at the same time.
For more information please see the contributor guide

In response to this:

@neolit123 thanks, I will assign it to myself
/assign

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[manparvesh]

Oh, I can't do that. Can you please assign me this issue?
I am not sure how this works

[neolit123]

you are not a member of the kubernetes-sigs organization so you cannot be assigned.
just sent a PR, thanks.

/lifecycle active

[manparvesh]

Oh I understand. I will send a PR.
Thanks

[BenTheElder]

Thanks for the PR :-) this check should be much better when the user uses multiple KUBECONFIG 🎉

For future reference there is an edgecase now around partial match where the file name later for some reason becomes a directory and is referenced in KUBECONFIG, but this case seems pretty unlikely...

We could get arbitrarily complex with this check (what about if there's a different equivalent path strinf specifying the same file?) and it wouldn't really be worth it (I'm guessing, maybe we change our mind later based on usage) because it's just a helpful reminder and we can't check your other open terminals anyhow.

Hopefully it's good enough now 😄