A restore by a normal user always warned that file ownership was not
preserved, even when every entry came out with its recorded owner and
group. The owner and group each restored entry has on disk are now
compared with the recorded ones, and the warning is printed once if any
differ. The comparison is made on disk because on macOS, and in a setgid
directory on Linux, a new entry takes the group of its directory, not
the user's.
Judgement call: an entry that is not on disk after the restore is not compared.
Unverified: not run on a Mac; the directory-group test runs only as root.
Model: opus-5-5
sneak