t4138: stop losing return codes of git commands

In a pipe, only the return code of the last command is used. Thus, all
other commands will have their return codes masked. Rewrite pipes so
that there are no git commands upstream so that we will know if a
command fails.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4138-apply-ws-expansion.sh

@@ -17,8 +17,8 @@ test_expect_success setup '
 	printf "\t%s\n" 1 2 3 >after &&
 	printf "%64s\n" a b c >>after &&
 	printf "\t%s\n" 4 5 6 >>after &&
-	git diff --no-index before after |
-		sed -e "s/before/test-1/" -e "s/after/test-1/" >patch1.patch &&
+	test_expect_code 1 git diff --no-index before after >patch1.patch.raw &&
+	sed -e "s/before/test-1/" -e "s/after/test-1/" patch1.patch.raw >patch1.patch &&
 	printf "%64s\n" 1 2 3 4 5 6 >test-1 &&
 	printf "%64s\n" 1 2 3 a b c 4 5 6 >expect-1 &&
 
@@ -33,8 +33,8 @@ test_expect_success setup '
 		x=$(( $x + 1 ))
 	done &&
 	printf "\t%s\n" d e f >>after &&
-	git diff --no-index before after |
-		sed -e "s/before/test-2/" -e "s/after/test-2/" >patch2.patch &&
+	test_expect_code 1 git diff --no-index before after >patch2.patch.raw &&
+	sed -e "s/before/test-2/" -e "s/after/test-2/" patch2.patch.raw >patch2.patch &&
 	printf "%64s\n" a b c d e f >test-2 &&
 	printf "%64s\n" a b c >expect-2 &&
 	x=1 &&
@@ -56,8 +56,8 @@ test_expect_success setup '
 		x=$(( $x + 1 ))
 	done &&
 	printf "\t%s\n" d e f >>after &&
-	git diff --no-index before after |
-	sed -e "s/before/test-3/" -e "s/after/test-3/" >patch3.patch &&
+	test_expect_code 1 git diff --no-index before after >patch3.patch.raw &&
+	sed -e "s/before/test-3/" -e "s/after/test-3/" patch3.patch.raw >patch3.patch &&
 	printf "%64s\n" a b c d e f >test-3 &&
 	printf "%64s\n" a b c >expect-3 &&
 	x=0 &&
@@ -84,8 +84,8 @@ test_expect_success setup '
 		printf "\t%02d\n" $x >>after
 		x=$(( $x + 1 ))
 	done &&
-	git diff --no-index before after |
-	sed -e "s/before/test-4/" -e "s/after/test-4/" >patch4.patch &&
+	test_expect_code 1 git diff --no-index before after >patch4.patch.raw &&
+	sed -e "s/before/test-4/" -e "s/after/test-4/" patch4.patch.raw >patch4.patch &&
 	>test-4 &&
 	x=0 &&
 	while test $x -lt 50