One of the strengths of the xar format is its metadata capabilities. However, it's rather difficult to expose particular pieces of metadata at whim. (For instance, backup software would want the checksums for arbitrary files.) A quick hack is below, enough to allow me to get metadata with a bash util designed to keep archival backups.

Oh, to expose metadata, the -v flag must be added to raise 'verbose' a level, due to the odd verbosity kludge in print_file().

I think it would be possible to do something like this with the existing include/exclude options when used with - t.