Make the binary dynamically determine whether it is a kubectl plugin

[inteon]

fixes #38

See https://krew.sigs.k8s.io/docs/developer-guide/develop/best-practices/

TODO: I would like to get some feedback on the kubectl cert-manager autocomplete functionality.
UPDATE: autocomplete works as expected, additional improvements can be made in a separate PR

This PR adds a new completion command based on @maelvls' instructions to make kubectl completion work (cert-manager/cert-manager#4657): ./kubectl-cert-manager completion kubectl --help

[cert-manager-prow]

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[ThatsMrTalbot]

Looks to work for me, help prints the correct binary and autocomplete works (assuming you have that set up as per cert-manager/cert-manager#4657)

One thing we could do though, is if we detect the binary name, could we detect kubectl_complete-cert_manager also and remove the need for the script? This could be a follow up improvement, dont think that it should block this

[maelvls]

I've tried it, I had to rename the binary after running go install since the go.mod module name ends with cmctl:

go install . && mv $(go env GOPATH)/bin/{cmctl,kubectl-cert_manager}

Installing the "completion" is... weird. It is a shim rather than a completion script. I think I prefer Adam's idea. With Adam's idea, instead of:

kubectl cert-manager completion kubectl >$(go env GOPATH)/bin/kubectl_complete-cert-manager
chmod +x $(go env GOPATH)/bin/kubectl_complete-cert-manager

It would be:

ln -s $(which kubectl-cert_manager) $(dirname $(which kubectl-cert_manager))/kubectl_complete-cert-manager

No script needs to be created, and completion kubectl is no longer necessary 👍 Although it would be good to have a note in the --help with a link that explains how to enable completion.

What do you think?

[inteon]

Installing the "completion" is... weird. It is a shim rather than a completion script. I think I prefer Adam's idea. What do you think?

I'll investigate if this is easily doable.

[inteon]

I propose that we improve the completion logic in a separate PR.

[maelvls]

Does this have to do with "making the binary dynamically determine whether it is a kubectl plugin"?

Inlining these Long paragraphs is a good idea, but it makes it extra hard to review the actual changes.

[inteon]

Yes, I inlined these paragraphs because sometimes we call build.WithTemplate(setupCtx, which takes the setupCtx argument to determine if it is running as cmctl or kubectl cert-manager.