FIX: test-lib: Print differences when test_expect_output fails.

When the command-under-test fails with a non-zero exit code, neither the different exit code nor any output differences are printed. Also, there's a lot of duplication between test_expect_output and test_expect_code_and_output. So, let's fix both by delegating the first to the latter.

tests/test-lib.sh

@@ -264,25 +264,7 @@ test_expect_success () {
 test_expect_output () {
 	test "$#" = 2 ||
 	error "bug in the test script: not 2 parameters to test-expect-output"
-	if ! test_skip "$@"
-	then
-		say >&3 "expecting success and output: $2"
-		test_run_ "$2"
-		if [ "$?" = 0 -a "$eval_ret" = 0 ]
-		then
-			cmp_output=$(test_cmp expect output)
-			if [ "$?" = 0 ]
-			then
-				test_ok_ "$1"
-			else
-				test_failure_ "$@" "
-$cmp_output"
-			fi
-		else
-			test_failure_ "$@"
-		fi
-	fi
-	echo >&3 ""
+	test_expect_code_and_output 0 "$@"
 }
 
 test_expect_code_and_output () {
@@ -290,7 +272,11 @@ test_expect_code_and_output () {
 	error "bug in the test script: not 3 parameters to test-expect-code-and-output"
 	if ! test_skip "$@"
 	then
+		if [ "$1" = 0 ]; then
+			say >&3 "expecting success and output: $3"
+		else
 			say >&3 "expecting exit code $1 and output: $3"
+		fi
 		test_run_ "$3"
 		if [ "$?" = 0 -a "$eval_ret" = "$1" ]
 		then