Aryeh Gregor wrote:
Alternatively, if it's rolled out for actual content and screw anyone who doesn't support it, that could be done incrementally, with the percentage of protocol-relative links starting out extremely small and slowly increasing over time if no complaints come in. Then the damage should be as minimal as possible. Or the protocol-relative links could be deployed deterministically based on page name, and then if there's a problem all the affected pages could be purged (but you'd still want to start slow to avoid having to do huge purges).
I think the next step, after the log comparison test we both suggested, would be to set $wgLogo to a protocol-relative URL. A missing logo wouldn't actually break anything, but you _bet_ people would notice it.