delta-apply: fix sign extension

We compute offsets by executing `off |= (*delta++ << 24)` for
multiple constants, where `off` is of type `size_t` and `delta`
is of type `unsigned char`. The usual arithmetic conversions (see
ISO C89 §3.2.1.5 "Usual arithmetic conversions") kick in here,
causing us to promote both operands to `int` and then extending
the result to an `unsigned long` when OR'ing it with `off`.
The integer promotion to `int` may result in wrong size
calculations for big values.

Fix the issue by making the constants `unsigned long`, causing both
operands to be promoted to `unsigned long`.

Author: pks-t

src/delta-apply.c

@@ -90,13 +90,13 @@ int git__delta_apply(
 			size_t off = 0, len = 0;
 
 			if (cmd & 0x01) off = *delta++;
-			if (cmd & 0x02) off |= *delta++ << 8;
-			if (cmd & 0x04) off |= *delta++ << 16;
-			if (cmd & 0x08) off |= *delta++ << 24;
+			if (cmd & 0x02) off |= *delta++ << 8UL;
+			if (cmd & 0x04) off |= *delta++ << 16UL;
+			if (cmd & 0x08) off |= *delta++ << 24UL;
 
 			if (cmd & 0x10) len = *delta++;
-			if (cmd & 0x20) len |= *delta++ << 8;
-			if (cmd & 0x40) len |= *delta++ << 16;
+			if (cmd & 0x20) len |= *delta++ << 8UL;
+			if (cmd & 0x40) len |= *delta++ << 16UL;
 			if (!len)		len = 0x10000;
 
 			if (base_len < off + len || res_sz < len)