Function renamed_unit_name 

pub fn renamed_unit_name(
    old_rel: &Path,
    old_name: &str,
    new_rel: &Path,
) -> Option<String>

#302: the qualified name a file moved from old_rel to new_rel should now declare, preserving whichever single-file/multi-file arrangement old_rel used to satisfy against old_name — for the LSP’s workspace/willRenameFiles handler.