Append --force-update for specific helm versions.

[wi1dcard]

This PR contains 1 bug fix and 1 change:

• Fix the helm version comparison. As @tyrken mentioned in Fix helm version checking #1493, I'm trying to use the semver package to parse, compare, and process the helm version string.
• Use option --force-update in helm repo add, ONLY when the Helm version is >= 3.3.2 and < 3.3.4 (ref helmfile repos attempts to re-add already added repo #1489 and Fixing issue with idempotent repo add helm/helm#8777).

[voron]

As @RothAndrew mentioned here, it may be a valid case to use --force-update with helm versions 3.3.4+ too, when you're really need to update repository via helmfile. My propose is to get following syntax in helmfile:

helmDefaults:
  repoForceUpdate: false
...
repositories:
  - name: git-based-repo
    url: git+ssh://git@github.com/roboll/helmfile@?ref=<FREQUENTLY_CHANGED_OR_DYNAMIC_REF>
    forceUpdate: true

WDYT?
We don't need this option with helm <3.3.2, but with 3.3.2+ (and 3.3.4+ too) it may be better to let helmfile user decide what to do with it.

[wi1dcard]

Hi @voron , I didn't realized that we can use a URL with the specific ref of version. Hmmm, I think that would be a great case of showing why we need to leave the option and let the users decide. What about the default value of repositories.*.forceUpdate? We may have 3 choices:

1. The default value of repositories.*.forceUpdate is always false.
2. The default value is determined based on the Helm version, >=3.3.2 && <3.3.4 -> true, otherwise -> false.
3. The default value is determined based on the Helm version, >=3.3.2 -> true, otherwise -> false.
4. The default value of repositories.*.forceUpdate is helmDefaults.repoForceUpdate, and the default value of latter one can be one of above.

Personally I prefer 4th + 1st or just the third one. Because:

With 4th + 1st, we keep the default behavior as secure as possible without adding any additional flags, and the users who use the specific helm versions can simplely change the behavior for all repos in one place helmDefaults.repoForceUpdate.

With the third, we can add the --force-update under the hood and do not have to "break" anything. Users won't notice that there's any change either using helm < 3.3.2 or helm > 3.3.4.

What do you think?

cc @mumoshu

[voron]

I vote for 4th+1st:

The default value of repositories.*.forceUpdate is helmDefaults.repoForceUpdate
The default value of helmDefaults.repoForceUpdate is false

It's helm "responsibility" to break this thing, I don't see reasons to hide it from helmfile user. We need to provide an ability to adjust this option when required, w/o any "smart" staff IMHO.

[mumoshu]

I vote for 4th + 1st, too. I thought 4th + 2nd or 3rd would be the best before seeing helm/helm#8777 - apparently the Helm team "fixed" the regression issue very quickly 👍

[mumoshu]

This LGTM as its current state and I'm merging this as it only enhances the current implementation. Thank you so much for your continued effort @wi1dcard!

I'll leave the implementation of the ability to expose --force-update configurable to another PR(s).