If tarup.sh is run with -f, reflect that in filenames

Serves as a hint to avoid accidentally uploading files created
with -f anywhere (not that I'd ever make such a mistake ...)
make diagnostic output consistent with one used by buildrump.sh
Rewrite compressing as a loop

It's not really any smaller or more obvious when written as a loop, but
noneless one of those ridiculous CS things where opencoding something
just really irks thee.