use isxdigit() for checking if a character is a hexadecimal digit

Use the standard function isxdigit() to make the intent clearer and
avoid using magic constants.

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

Author: rscharfe

sha1_name.c

@@ -749,7 +749,7 @@ static int get_describe_name(const char *name, int len, unsigned char *sha1)
 
 	for (cp = name + len - 1; name + 2 <= cp; cp--) {
 		char ch = *cp;
-		if (hexval(ch) & ~0377) {
+		if (!isxdigit(ch)) {
 			/* We must be looking at g in "SOMETHING-g"
 			 * for it to be describe output.
 			 */

transport.c

@@ -117,7 +117,7 @@ static void insert_packed_refs(const char *packed_refs, struct ref **list)
 			return;
 		}
 
-		if (hexval(buffer[0]) > 0xf)
+		if (!isxdigit(buffer[0]))
 			continue;
 		len = strlen(buffer);
 		if (len && buffer[len - 1] == '\n')