ManifestJarWriter manages writing the manifest by hand, including wrapping lines, etc. etc. This code was copied from plexus-archiver when we stopped depending on plexus-archiver.
But AFAIK there's no reason to do that by hand; java.util.jar.Manifest can take care of all of that for us. Still, it's creepy that they did all of that work, so maybe there was a good reason for it...?