Dealing with NULs is not always safe with tr. On Solaris,
incoming NULs are silently deleted by both the System V and
UCB versions of tr. When converting to NULs, the System V
version works fine, but the UCB version silently ignores the
request to convert the character.
This patch changes all instances of tr using NULs to use
"perl -pe 'y///'" instead.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>