use preprocessing to handle the first time apply with inventorypolicy

[Liujingfang1]

With inventory-policy flags added, users have two options: strict and adopt. strict means an object can be updated/pruned only when the owning-inventory annotation matches with the current inventory object. adopt means that an object can be updated/pruned when the owning-inventory annotation matches or this annotation is not present. The default option is strict.

When package was applied by previous version of kpt, which doesn't have the inventory-policy flag. We need to handle the first time apply when user switches to the new version of kpt. In the first time apply, the inventory-policy should be adopt so that the resources will be added the owning-inventory annotation.

In this change, the first time apply is detected by checking the label "apps.kubernetes.io./managed-by". If this label is missing, we treat it as the first time apply and add this label to the inventory object.

This PR depends on kubernetes-sigs/cli-utils#316

[seans3]

Small question about consts

[Liujingfang1]

@seans3 Addressed the comments. It's ready for another review.

[mortent]

I think this looks good. Would the use of cobra command wrappers be simplified if we just implement the commands in kpt instead of cli-utils?
And is there a way we can add tests for some of this?

[Liujingfang1]

I think this looks good. Would the use of cobra command wrappers be simplified if we just implement the commands in kpt instead of cli-utils?

Yes, it would simplify the implementation a lot. We don't need to inject the preprocessing from the wrapper to the actual cli.

And is there a way we can add tests for some of this?

I'm also thinking about this. The existing e2e test, specifically the one for testing kpt live of different kpt versions, covers the first-time apply case. Besides that, we can add a unit test for the PreProcess function.

[Liujingfang1]

@mortent I added unit tests for the pre processing function. PTAL

[seans3]

looks good to me. I'll let Morten also sign-off.

[seans3]

/lgtm