t5520: reduce commom lines of code

These two tests are almost similar and thus can be folded in a for-loop.

Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Mehul Jain <mehul.jain2029@gmail.com>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5520-pull.sh

@@ -298,15 +298,13 @@ test_expect_success 'pull --rebase --no-autostash & rebase.autostash unset' '
 	test_pull_autostash_fail --rebase --no-autostash
 '
 
-test_expect_success 'pull --autostash (without --rebase) should error out' '
-	test_must_fail git pull --autostash . copy 2>err &&
-	test_i18ngrep "only valid with --rebase" err
-'
-
-test_expect_success 'pull --no-autostash (without --rebase) should error out' '
-	test_must_fail git pull --no-autostash . copy 2>err &&
-	test_i18ngrep "only valid with --rebase" err
-'
+for i in --autostash --no-autostash
+do
+	test_expect_success "pull $i (without --rebase) is illegal" '
+		test_must_fail git pull $i . copy 2>err &&
+		test_i18ngrep "only valid with --rebase" err
+	'
+done
 
 test_expect_success 'pull.rebase' '
 	git reset --hard before-rebase &&