Add --prev-app to delete command

[neil-hickey]

• This PR assumes the user wants to see the changeset diff on the cli
  also when providing a --prev-app. Hence the use of the Factory twice.
• The case of both existing is interesting, for now it ignores the
  --prev-app existing if --app exists
• Nothing inside recorded_app.go needs to change with this pattern

Signed-off-by: Neil Hickey nhickey@vmware.com

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?

Additional Notes for your reviewer:

Review Checklist:

• Follows the developer guidelines
• Relevant tests are added or updated
• Relevant docs in this repo added or updated
• Relevant carvel.dev docs added or updated in a separate PR and there's
  a link to that PR
• Code is at least as readable and maintainable as it was before this
  change

Additional documentation e.g., Proposal, usage docs, etc.:

[neil-hickey]

Some things to note:

1. I chose to use the Factory twice - allows most of the code to remain as is in delete.go and recorded_app.go doesn't need to change at all.
2. This may introduce other problems I am not fully thinking through right now, I wanted to check with @praveenrewar and others to see what you all thought.
3. I wanted the user to see the diff and hit yes etc even for a --prev-app app. So this factory request for each app made most sense in that context as it shows this diff and confirmation already

Interesting case:
App1 exists, App2 exists

kapp delete -a App1 --prev-app App2

What would you expect the behaviour to me? Given that App2 should have been migrated and not exist at the same time, I expect App1 to be deleted and App2 to be ignored.

Any UX opinions on this case?

[praveenrewar]

I chose to use the Factory twice - allows most of the code to remain as is in delete.go and recorded_app.go doesn't need to change at all.

I had something similar in my mind, so I am actually happy with this approach.

App1 exists, App2 exists
kapp delete -a App1 --prev-app App2
What would you expect the behaviour to me?

Given that App2 should have been migrated and not exist at the same time, I expect App1 to be deleted and App2 to be ignored.

I totally agree. We should just ignore App2 in this case as this scenario shouldn't have happened.

[praveenrewar]

LGTM!

[100mik]

LGTM!

[sethiyash]

Looks Good.

[renuy]

Available as part v0.48.0