I have another use-case for this request.
My application is deployed several times as different apps in Heroku and elsewhere. Let’s say one is a staging app, another production. The only differences between the two is that they point to different resources, such as staging vs. production database, twilio account, etc. Now also Redis. Both applications are running in the production environment, so I can’t differentiate based on that in my redis.yml file. For all other resources, I’ve been able to use environment variables to point to different URLs for different instances of the application. For Redis, I can’t do that.
I agree that this is not a matter of security, and I agree that many users just want to put the URL in that config file, so I would certainly still allow that. But I’m sure I’m not the only one differentiating staging and production app resource by environment variable, and I think this would help lots of people.