repair: use rawvfs when copying extra store files If we use the normal vfs, store encoding will be applied when we .join() the path to be copied. This results in attempting to copy a file that (likely) doesn't exist. Using the rawvfs operates on the raw file path, which is returned by vfs.readdir(). Users at Mozilla are encountering this, as I've instructed them to run `hg debugupgraderepo` to upgrade to generaldelta. While Mercurial shouldn't deposit any files under .hg/store that require encoding, it is possible for e.g. .DS_Store files to be created by the operating system.