t0004 (unwritable files): simplify error handling

Instead of

	... normal test script ...
	status=$?
	... cleanup ...
	(exit $status)

set up cleanup commands with test_when_finished.  This makes the
test script a little shorter, and more importantly, it ensures errors
during cleanup are reported.
Signed-off-by: NJonathan Nieder <jrnieder@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t0004-unwritable.sh

@@ -16,53 +16,29 @@ test_expect_success setup '
 '
 
 test_expect_success POSIXPERM,SANITY 'write-tree should notice unwritable repository' '
-
-	(
-		chmod a-w .git/objects .git/objects/?? &&
-		test_must_fail git write-tree
-	)
-	status=$?
-	chmod 775 .git/objects .git/objects/??
-	(exit $status)
-
+	test_when_finished "chmod 775 .git/objects .git/objects/??" &&
+	chmod a-w .git/objects .git/objects/?? &&
+	test_must_fail git write-tree
 '
 
 test_expect_success POSIXPERM,SANITY 'commit should notice unwritable repository' '
-
-	(
-		chmod a-w .git/objects .git/objects/?? &&
-		test_must_fail git commit -m second
-	)
-	status=$?
-	chmod 775 .git/objects .git/objects/??
-	(exit $status)
-
+	test_when_finished "chmod 775 .git/objects .git/objects/??" &&
+	chmod a-w .git/objects .git/objects/?? &&
+	test_must_fail git commit -m second
 '
 
 test_expect_success POSIXPERM,SANITY 'update-index should notice unwritable repository' '
-
-	(
-		echo 6O >file &&
-		chmod a-w .git/objects .git/objects/?? &&
-		test_must_fail git update-index file
-	)
-	status=$?
-	chmod 775 .git/objects .git/objects/??
-	(exit $status)
-
+	test_when_finished "chmod 775 .git/objects .git/objects/??" &&
+	echo 6O >file &&
+	chmod a-w .git/objects .git/objects/?? &&
+	test_must_fail git update-index file
 '
 
 test_expect_success POSIXPERM,SANITY 'add should notice unwritable repository' '
-
-	(
-		echo b >file &&
-		chmod a-w .git/objects .git/objects/?? &&
-		test_must_fail git add file
-	)
-	status=$?
-	chmod 775 .git/objects .git/objects/??
-	(exit $status)
-
+	test_when_finished "chmod 775 .git/objects .git/objects/??" &&
+	echo b >file &&
+	chmod a-w .git/objects .git/objects/?? &&
+	test_must_fail git add file
 '
 
 test_done