kpt: pkg update fails to update Kptfile

[michaelvl]

Expected behavior

A kpt pkg get followed by a kpt pkg update --strategy force-delete-replace results in a Kptfile that has the git information as specified in the kpt pkg update but the pipeline section of the Kptfile is from the initial kpt pkg get and not the pipeline from the kpt pkg update. The consequence is that one cannot update the package pipeline.

The problem also applies to strategy fast-forward.

Tested using kpt version 1.0.0-beta.38 and 1.0.0-beta.43.

Detailed description of the problem and steps to reproduce it can be found here: https://github.com/michaelvl/kpt-test

[michaelvl]

A test-case that validates the problem can be found here: https://github.com/GoogleContainerTools/kpt/pull/4030