Unfortunately, while {read,write}_in_full do take into account
zero-sized reads/writes; their die and whine variants do not.

I have a repository where there are zero-sized files in
the history that was triggering these things.
Signed-off-by: NEric Wong <normalperson@yhbt.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>