Using -d is odd, because we normally reserve that for a database
argument, so rename it to -v and add long version --verbose.

Also, reduce it to emit one line per file checked rather than one line
per block.

Per a complaint from Michael Banck.

Author: Yugo Nagata <nagata@sraoss.co.jp>
Reviewed-by: Michael Banck <michael.banck@credativ.de>
Discussion: https://postgr.es/m/20180827113411.GA22768@nighthawk.caipicrew.dd-dns.de