fix bsd shell negation

On some shells (notably /bin/sh on FreeBSD 6.1), the
construct

  foo && ! bar | baz

is true if

  foo && baz

whereas for most other shells (such as bash) is true if

  foo && ! baz

We can work around this by specifying

  foo && ! (bar | baz)

which works everywhere.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/t5302-pack-index.sh b/t/t5302-pack-index.sh
index b88b5bb..09fd917 100755
--- a/t/t5302-pack-index.sh
+++ b/t/t5302-pack-index.sh
@@ -65,7 +65,7 @@
 
 have_64bits=
 if msg=$(git verify-pack -v "test-3-${pack3}.pack" 2>&1) ||
-	! echo "$msg" | grep "pack too large .* off_t"
+	! (echo "$msg" | grep "pack too large .* off_t")
 then
 	have_64bits=t
 else