[feat] Ability to load secrets from environment variables

[gothka]

Hey! Since docker v20.10.x there's a way to load docker secret using env vars when buildkit is enabled. Can it supported by skaffold? I can't find any reference in the docs, but i found this allowing to read secrets from a file.

[alex-dixon]

I think this may help with #6079 also, where users are looking to reference a secret in the home directory but cannot expand env vars like $HOME.

[ahmetb]

@abhishiekgowtham this seems doable if we can add env: field and make it mutually exclusive with src: in the linked schema section.

@alex-dixon I doubt this help with variable expansion in src: field but you could do export MY_ENV="$(cat $HOME/file)" while running skaffold (with a tool like direnv)?

[gothka]

Thanks for working/adding the feature @ahmetb! 👍

[ahmetb]

@abhishiekgowtham no problem! have you had a chance to build from the repo and try it out?

[gothka]

Yes, it actually seems to work.