Cause: Neither documentation nor cmd help talked about insecure connections to the secured registry. Errors used to be hard to decipher when user attempted to prune secured registry with bad CA certificate.
Consequence: Users had troubles running image prune against (in)secured registries.
Fix: Errors are now printed with hints, cmd help has been updated, new flags have been provided to allow for insecure fall-back.
Result: User can now easily enforce both secure and insecure connection. He will also be able to understand https errors and what to do when he hits them.