Skaffold should not validate kpt version

[ericzzzzzzz]

Information

• Skaffold currently has a validation against kpt version on kpt render, deployer

  skaffold/pkg/skaffold/schema/validation/validation.go

  Line 104 in 285c697

  func validateKptRendererVersion(cfg *parser.SkaffoldConfigEntry, dc latest.DeployConfig, rc latest.RenderConfig) (cfgErrs []ErrorWithLocation) {

• The validation was added due to a change introduced by kpt where kpt fn source xxx include meta-resources(Kptfile) content in its output
• If skaffold deploys the output with a non-kpt deployer, the deploy attempt will fail
• Even we don't want deployments to fail, we shouldn't set maxVersion limit for kpt, or we may just don't use kpt beta version at all .
  • Setting the maxVersion can prevent users from new kpt, users have to make a choice between to use skaffold and using new version kpt for new features and bug fixes. This is a bit frustrating.
  • Also, if even users want to sacrifice the new stuff in a higher version of kpt, downgrading tool usually is not very pleasant experience
• We should remove the validation for kpt version and remove extra Kptfile content in the output manifest on skaffold end.

[ericzzzzzzz]

• Kpt has a deprecated flag to toggle whether including Kptfile content into output for kpt fn source .. command, this is deprecated and not working with false

[ericzzzzzzz]

Let's include "upgrading kpt version in skaffold image" into the issue scope as well .