t: do not hide Git's exit code in tests using 'nul_to_q'

Git should not be on the left-hand side of a pipe, because it hides the exit
code, and we want to make sure git does not fail.

Fix all invocations of 'nul_to_q' (defined in /t/test-lib-functions.sh) using
this pattern. There is one more occurrence of the pattern in t9010-svn-fe.sh
which is too evolved to change it easily.

All remaining test code that does not adhere to the pattern can be found with
the following command:
git grep -E 'git.*[^|]\|($|[^|])'
Helped-by: NJeff King <peff@peff.net>
Signed-off-by: NLars Schneider <larsxschneider@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t1300-repo-config.sh

@@ -957,13 +957,15 @@ Qsection.sub=section.val4
 Qsection.sub=section.val5Q
 EOF
 test_expect_success '--null --list' '
-	git config --null --list | nul_to_q >result &&
+	git config --null --list >result.raw &&
+	nul_to_q <result.raw >result &&
 	echo >>result &&
 	test_cmp expect result
 '
 
 test_expect_success '--null --get-regexp' '
-	git config --null --get-regexp "val[0-9]" | nul_to_q >result &&
+	git config --null --get-regexp "val[0-9]" >result.raw &&
+	nul_to_q <result.raw >result &&
 	echo >>result &&
 	test_cmp expect result
 '

t/t7008-grep-binary.sh

@@ -141,7 +141,8 @@ test_expect_success 'grep respects not-binary diff attribute' '
 	test_cmp expect actual &&
 	echo "b diff" >.gitattributes &&
 	echo "b:binQary" >expect &&
-	git grep bin b | nul_to_q >actual &&
+	git grep bin b >actual.raw &&
+	nul_to_q <actual.raw >actual &&
 	test_cmp expect actual
 '