Make the kubeseal CLI have a skinny main

[josvazg]

Description of the change

The CLI had way too much code within the main package.

This change moves most of the kubeseal CLI code to a package "pkg/kubeseal", leaving a simple "main" which is only concerned with CLI flags and other command line perks.

Note that the changes are minimal, and only functions affected by the split of code between main and the package are really affected. The rest is code copied to another package.

Other changes included:

• Flag fields needed to become public, and this are upper case now.
• There is a new NewConfig() function now.
• VERSION handling is handled by main completely and is out of the Flags struct now.

Benefits

Code in the new pkg is accesible from other packages and can be further refactored and improved.

Possible drawbacks

This is still a mostly mechanical code move, it does not yet address making the kubeseal code look and feel like a proper library to be consumed by code outside of a CLI context. This was left out of scope intentionally to make progress on smaller incremental steps.

Additional information

Once this code is merged, the intent going forward is to start refactoring things out of the big Run function in small steps. The expectation of the final result is that a smaller (and skinny) version of such "run" might go back to the main code but it will only decide what operations or behaviors of kubeseal will be invoked by each CLI execution. Many of those behaviors or operations will become new functions within kubeseal. Hopefully we can get rid of using the Flags struct within kubeseal.

[josvazg]

Tip: The diff might be more confusing that actually looking at the resulted main.go and main_test.go now to have a sense of what has remained there. The "pkg/kubeseal" code is mostly copy& paste from main except for those bits that could not be moved.

See main final state as a whole here:

[alvneiayu]

LGTM

[josvazg]

I found a weird bug on the refactor and it ended up being because goimports had changed the imports in the moved code and picked the wrong import for scheme, choosing the local package over a dependency ("k8s.io/client-go/kubernetes/scheme")

In order to detect other instances of goimports making wrong choices, I did a comparison of old and new imports. I expect that new imports on the main AND kubeseal be the same as the old main. Same for tests, new test files combined should import the same things as the old main_test code did.

$ cat /tmp/imports-new-main.txt /tmp/imports-new-kubeseal.txt | sort -u | grep -v '^$' > /tmp/new-code-imports
$ sort -u < /tmp/imports-old-main.txt |grep -v '^$' > /tmp/expected-code-imports
$ diff /tmp/expected-code-imports /tmp/new-code-imports 
13a14
> 	"github.com/bitnami-labs/sealed-secrets/pkg/kubeseal"
28c29
< 	"k8s.io/klog/v2"
---
> 	"k8s.io/klog"

This happened because goimports knew it needed to import a klog package ,but it did not know it had to be version 2.

Note the github.com/bitnami-labs/sealed-secrets/pkg/kubeseal is expected on the new main and not the old, that is the code we moved away.

Test code showed no differences, so we are fine there:

$ cat /tmp/imports-new-main_test.txt /tmp/imports-new-kubeseal_test.txt | sort -u | grep -v '^$' > /tmp/new-test-imports
$ sort -u < /tmp/imports-old-main_test.txt |grep -v '^$' > /tmp/expected-test-imports
$ diff /tmp/expected-test-imports /tmp/new-test-imports 
$ 

Fix for klog/v2 coming up...

[alvneiayu]

LGTM