Feature Request

Summary

Add a flag which toggles between generating stable or nightly config.

Motivation

Currently crossgen only supports generating config to test on nightly. If someone want's to test on stable instead they have to manually change all the places which say nightly.

Expected Behavior

crossgen: current default is to generate nightly config crossgen --stable: create config for stable

There's currently only a handful of places where a switch would be needed. In .travis.yml and in https://github.com/yoshuawuyts/crossgen/blob/master/templates/lib/script.sh#L22

Drawbacks

Not sure how it might be implemented: some sort of templating or just bash conditionals?

Rationale and alternatives

The only other alternative is manual changes after running crossgen

Unresolved Questions

Should stable or nightly be the default. I'd consider changing this a breaking change.