https://github.com/rails/rails/pull/25667/files
That pull allows specifying e.g. protocol: :relative
when calling the asset_url
helper, instead of always using the request
protocol.
This is useful if, for example, you have a fragment that is served over both http and https and you want to use a relative protocol so the same cache can be used in both cases.
(Not sure if it’s necessary to send this to the mailing list too, but the contributing guide seems to say it is.)