Revert "zero pad the output filenames"
Revert "zero pad the output filenames"

This reverts commit c6bdd86fd4956ae8162fae038fd40b3ad2ac7362. It breaks
round-tripping, as reported in #173. (One could look for filenames with
and without zero padding, but I am not convinced that this is a good
idea. `ls -v` lists the files in the right order even without
zero-padding.)

entropia/tip-toi-reveng,entropia/tip-toi-reveng,entropia/tip-toi-reveng,entropia/tip-toi-reveng,entropia/tip-toi-reveng,entropia/tip-toi-reveng