[Bug-tar] --sparse is broken on filesystems where small files may have zero blocks

[Andrew J. Schorr]

Hi,

I have a Netapp file server, and their filesystem is able to contain
small files of up to 64 bytes in the inode without allocating any 
blocks.

This causes --sparse to corrupt files silently due to this patch:

http://git.savannah.gnu.org/cgit/tar.git/commit/?id=a9895fd20c957ce184091672f1623a5bedd82407

Please see this bug report:

https://bugzilla.redhat.com/show_bug.cgi?id=1024095

It is unfortunately not the case that an st_blocks value of zero
means that the file is empty on all filesystems.  I don't know if there
are any other exceptions besides Netapp.

Regards,
Andy