refactor: use bitsizeof() instead of 8 * sizeof()

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/sha1_file.c b/sha1_file.c
index 4576ff7..1d996a1 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1170,7 +1170,7 @@
 	size = c & 15;
 	shift = 4;
 	while (c & 0x80) {
-		if (len <= used || sizeof(long) * 8 <= shift) {
+		if (len <= used || bitsizeof(long) <= shift) {
 			error("bad object header");
 			return 0;
 		}