Implement render for kustomize

[arminbuerkle]

Relates to #1937 and #2957 for kustomize.

Description

Implements the render command for kustomize. Basically copied the way kubectl render works to kustomize to try it out. It works for my current purpose so i added a unit test.

If it looks good you can merge it, if someone else is already working on this feel free to close it.

User facing changes
Implements the render command for kustomize.

Next PRs.

n/a

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Includes unit tests
• Mentions any output changes.
• Adds documentation as needed: user docs, YAML reference, CLI reference. (Not needed?)
• Adds integration tests if needed. (Not needed?)

Reviewer Notes

• The code flow looks good.
• Unit test added.
• User facing changes look good.

Release Notes

- Implement `skaffold render` for `kustomize` deployer

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[arminbuerkle]

I'm not sure why Render doesn't have []Labeller as parameter. I think that's something that should get added in the future so the behaviour is similar to Deploy.

[nkubala]

it should have it. looks like maybe I forgot to put it in there when I added the boilerplate a while back.

[codecov]

Codecov Report

Merging #3110 into master will decrease coverage by 0.03%.
The diff coverage is 41.66%.

Impacted Files	Coverage Δ
pkg/skaffold/deploy/kustomize.go	71.63% <41.66%> (-2.57%)	⬇️

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[arminbuerkle]

@dgageot No sure whom to mention but is this PR going to make it? Should i keep it updated?

[dgageot]

Sorry @arminbuerkle, the team was quite busy launching version 1.0. I guess it's best to ping @nkubala

[arminbuerkle]

@nkubala friendly reminder that having this feature would be awesome and improve the gitops workflow with kustomize mentioned in #1937 & #2957

[nkubala]

hey @arminbuerkle, thanks for the contribution and really sorry it took me ages to get to you on this one!

I implemented this in #2911 a while ago, but closed it to split it up into smaller PRs and never got it back in. what you have here is very close to my original PR, but can you have a look at my implementation there and try and match what you have to that? specifically around the event handling and the labels being passed in to the renderer.

[arminbuerkle]

@nkubala PTAL. I fixed the event handling.

The labeling requires changing the Render interface and consequently all of its implementations. Not really something that should be in this PR.

I'm happy to submit a follow up PR that fixes labeling and introduces a cmd flag to allow setting labels when using skaffold render.

[alnr]

Is there any update on this PR?

[nkubala]

@arminbuerkle sorry for taking so long with this one. I tested this out and it seems to work well enough, so let's go ahead and get this in. we should definitely have a follow up PR to enable setting labels in Render - would you like to send that?

I opened #3482 to track.