t0008: silence error in subshell when using grep -v

In t0008 we use `grep -v` in a subshell, but expect that this command
will sometimes not match anything. This would cause grep(1) to return an
error code, but given that we don't run with `set -e` we swallow this
error.

We're about to enable `set -e`. Prepare for this by ignoring any errors.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

t/t0008-ignores.sh

@@ -122,8 +122,8 @@ test_expect_success_multiple () {
 	fi
 	testname="$1" expect_all="$2" code="$3"
 
-	expect_verbose=$( echo "$expect_all" | grep -v '^::	' )
-	expect=$( echo "$expect_verbose" | sed -e 's/.*	//' )
+	expect_verbose=$(echo "$expect_all" | grep -v '^::	' || true)
+	expect=$(echo "$expect_verbose" | sed -e 's/.*	//')
 
 	test_expect_success $prereq "$testname${no_index_opt:+ with $no_index_opt}" '
 		expect "$expect" &&