> if the rename fails mv blithely barrels into copying any volume of data

using rename happily averts ever inadvertently copying files, it
errors out instead.  if asked i'll be happy to post my mv-like bash
function that uses rename.  (what works best to post code and avoid
line breaks?  attach?  html blockquote?)  (markdown philosophy looks
compelling, but sadly it doesn't look like a markdown formatted
blockquote would survive simple email.)