Add "--normalize-manifests" flag as environment variable

[Anthon129]

Hi

I have a scenario using helmfile apply where the golang code behind the scenes runs helm diff upgrade followed by helm upgrade --install. I need to add the flag --normalize-manifests (to helm diff command) due to other reasons but this flag is unknown to helm upgrade (causing it to fail) and I am not able to apply separate individual flags to each of the commands. The flags applied to helm diff upgrade will be applied to helm upgrade.

Can we add an environment variable (i.e. HELM_DIFF_NORMALIZE_MANIFESTS=true) that would have the same effect as --normalize-manifests ?

Thanks

[Anthon129]

PR at #389

[frank-berlin]

+1