[Bug-tar] Is migration from listed-incremental format 0 to format 2 intended to work?

[Göran Uddeborg]

I've been doing backups with listed-incremental for many years.  When
I try to upgrade from a tar with dump format 0 (version 1.15.1) to
format 2 (version 1.17, Fedora 8 packaging) it tries to do a complete
backup.

Simple example to illustrate:

22:55 mimmi> mkdir tmp
22:55 mimmi> touch tmp/apa
22:55 mimmi> tar-1.15.1 --create --listed-incremental=#list --file=#.tar 
--verbose tmp
tmp/
tmp/apa
22:55 mimmi> tar --create --listed-incremental=#list --file=#.tar --verbose tmp
tmp/
tmp/apa

Format 2 has more data than format 0.  I guess newer tar makes some
conservative assumptions about the state at the time of the previous
backup which makes everything seem new.

Is this kind of migration not intended to work, or is it a bug?  Tar
1.17 reads format 0 as documented.  But I'm not sure what the point
with that is if it anyway behaves as if it started from scratch.