notes: move hex_to_bytes() to hex.c and export it

Make the function for converting pairs of hexadecimal digits to binary
available to other call sites.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

hex.c

@@ -35,6 +35,18 @@ const signed char hexval_table[256] = {
 	 -1, -1, -1, -1, -1, -1, -1, -1,		/* f8-ff */
 };
 
+int hex_to_bytes(unsigned char *binary, const char *hex, size_t len)
+{
+	for (; len; len--, hex += 2) {
+		unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
+
+		if (val & ~0xff)
+			return -1;
+		*binary++ = val;
+	}
+	return 0;
+}
+
 int get_sha1_hex(const char *hex, unsigned char *sha1)
 {
 	int i;