Support deleting previous objects in kubectl apply

[smarterclayton]

Description

When creating objects with kubectl apply, it is frequently desired to make changes to the config that remove objects and then re-apply and have those objects deleted. This feature will support pruning which deletes objects previously applied that no longer exist in the source config.

Progress Tracker

• Alpha
  • Write and maintain draft quality doc
    • During development keep a doc up-to-date about the desired experience of the feature and how someone can try the feature in its current state. Think of it as the README of your new feature and a skeleton for the docs to be written before the Kubernetes release. Paste link to Google Doc: DOC-LINK
  • Design Approval
    • Design Proposal. kubectl: implement kubectl apply --prune kubernetes#33075
    • Decide which repo this feature's code will be checked into. Not everything needs to land in the core kubernetes repo. REPO-NAME
    • Initial API review (if API). Maybe same PR as design doc. PR-NUMBER
      • Any code that changes an API (/pkg/apis/...)
      • cc @kubernetes/api
    • Identify shepherd (your SIG lead and/or kubernetes-pm@googlegroups.com will be able to help you). My Shepherd is: replace.me@replaceme.com (and/or GH Handle)
      • A shepherd is an individual who will help acquaint you with the process of getting your feature into the repo, identify reviewers and provide feedback on the feature. They are not (necessarily) the code reviewer of the feature, or tech lead for the area.
      • The shepherd is not responsible for showing up to Kubernetes-PM meetings and/or communicating if the feature is on-track to make the release goals. That is still your responsibility.
    • Identify secondary/backup contact point. My Secondary Contact Point is: replace.me@replaceme.com (and/or GH Handle)
  • Write (code + tests + docs) then get them merged. ALL-PR-NUMBERS
    • Code needs to be disabled by default. Verified by code OWNERS
    • Minimal testing
    • Minimal docs
      • cc @kubernetes/docs on docs PR
      • cc @kubernetes/feature-reviewers on this issue to get approval before checking this off
      • New apis: Glossary Section Item in the docs repo: kubernetes/kubernetes.github.io
    • Update release notes
• Beta
  • Testing is sufficient for beta
  • User docs with tutorials
    • Updated walkthrough / tutorial in the docs repo: kubernetes/kubernetes.github.io
    • cc @kubernetes/docs on docs PR
    • cc @kubernetes/feature-reviewers on this issue to get approval before checking this off
  • Thorough API review
    • cc @kubernetes/api
• Stable
  • docs/proposals/foo.md moved to docs/design/foo.md
    • cc @kubernetes/feature-reviewers on this issue to get approval before checking this off
  • Soak, load testing
  • detailed user docs and examples
    • cc @kubernetes/docs
    • cc @kubernetes/feature-reviewers on this issue to get approval before checking this off

FEATURE_STATUS is used for feature tracking and to be updated by @kubernetes/feature-reviewers.
FEATURE_STATUS: IN_DEVELOPMENT

More advice:

Design

• Once you get LGTM from a @kubernetes/feature-reviewers member, you can check this checkbox, and the reviewer will apply the "design-complete" label.

Coding

• Use as many PRs as you need. Write tests in the same or different PRs, as is convenient for you.
• As each PR is merged, add a comment to this issue referencing the PRs. Code goes in the http://github.com/kubernetes/kubernetes repository,
  and sometimes http://github.com/kubernetes/contrib, or other repos.
• When you are done with the code, apply the "code-complete" label.
• When the feature has user docs, please add a comment mentioning @kubernetes/feature-reviewers and they will
  check that the code matches the proposed feature and design, and that everything is done, and that there is adequate
  testing. They won't do detailed code review: that already happened when your PRs were reviewed.
  When that is done, you can check this box and the reviewer will apply the "code-complete" label.

Docs

• Write user docs and get them merged in.
• User docs go into http://github.com/kubernetes/kubernetes.github.io.
• When the feature has user docs, please add a comment mentioning @kubernetes/docs.
• When you get LGTM, you can check this checkbox, and the reviewer will apply the "docs-complete" label.

[davidopp]

I'm worried that we're starting to turn the features repo into another kubernetes/kubernetes issues repo, and it will become as undigestible.

I would argue this one doesn't meet the bar for going in the features repo.

[bgrant0607]

@mikedanese Isn't this done?

[grodrigues3]

@mikedanese can you update the checkboxes in the PR body with the parts that are finished.

[jaredbhatti]

Ping. Is there a docs PR for this?

[mikedanese]

Sorry, I missed this one.

Original issue: kubernetes/kubernetes#19805
Implementation: kubernetes/kubernetes#33075

There is command documentation like all of our other commands. Examples are being added in kubernetes/kubernetes#37397 at which point it will have as much documentation as any other kubectl flag. It will be labeled as alpha in the v1.5 kubectl help output, pending a sign off from @pwittrock .

cc @MrHohn

[pwittrock]

lgtm.

[jaredbhatti]

Ok. I'll mark this "no docs needed" Thanks!

[idvoretskyi]

@mikedanese @pwittrock can you confirm that this item targets beta in 1.6?

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