clonebundles: filter out invalid schemes instead of failing on them Previously, an invalid clonebundle scheme would result in a failed clone. By specifying a list of schemes we support, we can make sure adding a new scheme (like the one for inline clonebundles) does not result in clones failing for older clients.

clonebundles: demonstrate bad behaviour when unknown scheme is present

rhg: support `rhg files` with `ui.relative-paths=false`