Explicitly request GNU format. This will

disappear when GNU extended header keywords are working.

tests/multiv01.sh

@@ -19,13 +19,13 @@ for block in " 1" " 2" " 3" " 4" " 5" " 6" " 7" " 8" \
   done
 done >file2
 
-tar -c --multi-volume --tape-length=10 \
+tar -c --format=gnu --multi-volume --tape-length=10 \
   --listed-incremental=t.snar \
   -f t1-pipe.tar -f t2-pipe.tar ./file1 ./file2
 
 mkdir extract-dir-pipe
 dd bs=4096 count=10 if=t2-pipe.tar |
-PATH=$PATH ${TRUSS} tar -f t1-pipe.tar -f - \
+PATH=$PATH ${TRUSS} tar --format=gnu -f t1-pipe.tar -f - \
       -C extract-dir-pipe -x --multi-volume \
       --tape-length=10 --read-full-records