exit status patch

[jon stuart <jon@zomo.co.uk>]

Hi,

One of the filesystems that I run tarsnap across contains directories
that are reasonably volatile: files and subdirectories may be deleted by
a content management process during tarsnap's run.

Defiencies in this situation aside, I need to be able to distinguish
between tarsnap's surprise when files disappear between its feet and
other less expected errors, such as a network failure or similar. This
allows my monitoring to react accordingly and borrows from rsync's
similar provision of fine-grained exit status.

I drummed up this little patch to allow tarsnap's overall exit status
indicate what manner of error the bsdtar component encountered, if any.

  <http://gist.github.com/620099>

I'm no C hacker so would welcome any suggestions or criticism with this
tweak.

Regards, jon.