Merge branch 'jt/pack-header-lshift-overflow'

The code to decode the length of packed object size has been
corrected.

* jt/pack-header-lshift-overflow:
  packfile: avoid overflowing shift during decode

packfile.c

@@ -1068,7 +1068,7 @@ unsigned long unpack_object_header_buffer(const unsigned char *buf,
 	size = c & 15;
 	shift = 4;
 	while (c & 0x80) {
-		if (len <= used || bitsizeof(long) <= shift) {
+		if (len <= used || (bitsizeof(long) - 7) <= shift) {
 			error("bad object header");
 			size = used = 0;
 			break;