correct argument checking test for git hash-object

Because the file name given to stdin did not exist, git hash-object
fails to open it and exits with non-zero error code.

Thus the test may pass even if there is an error in argument checking.
Signed-off-by: NDmitry Potapov <dpotapov@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t1007-hash-object.sh

@@ -49,16 +49,16 @@ setup_repo
 # Argument checking
 
 test_expect_success "multiple '--stdin's are rejected" '
-	test_must_fail git hash-object --stdin --stdin < example
+	echo example | test_must_fail git hash-object --stdin --stdin
 '
 
 test_expect_success "Can't use --stdin and --stdin-paths together" '
-	test_must_fail git hash-object --stdin --stdin-paths &&
-	test_must_fail git hash-object --stdin-paths --stdin
+	echo example | test_must_fail git hash-object --stdin --stdin-paths &&
+	echo example | test_must_fail git hash-object --stdin-paths --stdin
 '
 
 test_expect_success "Can't pass filenames as arguments with --stdin-paths" '
-	test_must_fail git hash-object --stdin-paths hello < example
+	echo example | test_must_fail git hash-object --stdin-paths hello
 '
 
 # Behavior