feat(helm): Add --reset-then-reuse-values flag to 'helm upgrade'

[okhoshi]

What this PR does / why we need it:
When --reset-then-reuse-values is used on 'helm upgrade', the chart's values will be reset to the values of the deployed chart while the current release's values will be reused and merged with the values passed as argument (is any). --reset-values and --reuse-values flags take precedence over --reset-then-reuse-values, making it ignored if one or the other is also used.

This is a slight improvement over the many times suggested workaround of helm get values > v.yaml; helm upgrade --reset-values --values v.yaml in the sense that this flag allows for atomic operation.

Closes #8085
Closes #3957

If applicable:

• this PR contains documentation
• this PR contains unit tests
• this PR has been tested for backwards compatibility

[erickpeirson]

@bacongobbler How can we move this forward?

[bitjson]

This would really improve our workflow 👍

Tested, and PR works as expected. Is there any additional work or review which needs to be done before this can be merged?

[zombrie]

This is exactly what we need for our current chart situation... is this going to be merged soon?

[yaron2]

Please merge this. I can't stress enough how broken the current experience is.

[Ga13Ou]

Any idea why this simple, yet useful pull request isn't merged yet?

[voidtek]

This seems to solve my current headache. Any news?

[kostya2011]

Is there any news on this one?

[ldming]

This seems to solve my current headache. Any news?

[asauber]

This would be a huge help for getting the expected upgrade behavior when using --set. Can we merge this?

[asauber]

LGTM

[mamoit]

@okhoshi is there anything blocking this PR?

[okhoshi]

@mamoit No idea, not from my side at least. I don't have write access to this repo so I can't merge.

[mamoit]

Then @jglick, @asauber or @michi-covalent maybe?
Since they are the assigned reviewers.

[michi-covalent]

i don't have write access to the repo either. i just approved it because i love this PR ❤️

[joejulian]

I tested this and it works with every scenario I could think of. Approving but this still needs to pass CI.

[amannijhawan]

This is a quite useful PR, I have no special access either.

[0x2b3bfa0]

@joejulian, it already passes continuous integration checks.

[scottrigby]

LGTM. Thanks @okhoshi for this contribution 👏

A few extra kudos: the linked issues and PR description fully explain the use case for this new feature and the reasoning for this particular solution over existing workarounds. The PR includes automated tests, which are sensible and pass CI automation (since @joejulian last merged in main). This has been peer reviewed by other Helm community members, and reviewed now by two maintainers. Merging now, so this should be included in the next scheduled feature release. 🚀

[jglick]

should be included in the next scheduled feature release

Per https://github.com/helm/helm/releases/tag/v3.13.2

3.14.0 is the next feature release and [will] be on January 17, 2024.

Looking forward to finally having this fixed!

[voidtek]

Can't wait for it to be merged into the release-3.13 branch.
https://github.com/helm/helm/commits/release-3.13

@scottrigby : any blockers?

[mikael-floden]

OMG finally! Can't believe this is true, I have spent hours and hours explaining how helm is broken to every new developer. How --reuse-values breaks the system, ignoring all new values from the next version/release

People just didn't get it. I don't want to know how many weeks I have spent on users not understanding when you can and when you can't use --reuse-values.

This is how EVERYONE intuitively thinks it works, this parameter should be the default. The lack of this feature has hold back helm for to many years.

This is the "it always works parameter". Thanks you 🙏