This adds an -S --sort option which makes cp pass a comparison function to FTS,
FTS, ensuring that sources are visited and traversed in a predictable order.
order. This will help make certain test cases more reliable.
While here, fully switch boolean variables from int to bool, and clean
up the manual page
While here, add GNU-compatible long options where appropriate, fully
switch boolean variables from int to bool, and clean up the manual page
a little.
Sponsored by: Klara, Inc.