bug#70873: join --return-error-if-any-unmatched-lines

[Dan Jacobson]

join should have an option to return an error value in the shell's $?
if any lines are not matched.

Currently the man page doesn't even mention a return value. So it is not
set in stone yet.

Currently one must save -v output in a file then use test -s do detect
if there were any non-matched lines. And then exit one script with
non-zero. Big hassle.

join (GNU coreutils) 9.4