I was hoping that we cleverly redo the internals so that none of that
stuff changes. But you're right, if that's a pain we can sacrifice
compatibility; I doubt whether anyone will care.
As a matter of fact, that's the purpose of the --show-transformed
option: to inform the user about the actual filenames used when
extracting, so that's not only for testing.
But --show-transformed doesn't do that. It does something else:
$ tar -C /etc -cf /tmp/tarball passwd
$ mkdir /tmp/d
$ tar -C /tmp/d -xvf /tmp/tarball
passwd
If --show-transformed showed the actual file names used when extracting,
that last line would be "/tmp/d/passwd", not "passwd".
