Non-masked "variables" object to complement "secrets"

[rarkins]

Describe the proposed change(s).

Create a new configuration option called "variables" which behaves the same way as secrets except that its values are not masked in logs. It should be available in templates like this: {{ variables.FOO }}.

It is OK - but not recommended - for variables to have the same name as secrets.

[RahulGautamSingh]

global only?

[rarkins]

I can't think of any use case where making it repo-based is useful, so let's keep it as global only