hex: add oid_to_hex_r()

This function works just like sha1_to_hex_r, except that it takes a
pointer to struct object_id instead of a pointer to unsigned char.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -1193,6 +1193,7 @@ extern int get_oid_hex(const char *hex, struct object_id *sha1);
  *   printf("%s -> %s", sha1_to_hex(one), sha1_to_hex(two));
  */
 extern char *sha1_to_hex_r(char *out, const unsigned char *sha1);
+extern char *oid_to_hex_r(char *out, const struct object_id *oid);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern char *oid_to_hex(const struct object_id *oid);	/* same static buffer as sha1_to_hex */
 

hex.c

@@ -77,6 +77,11 @@ char *sha1_to_hex_r(char *buffer, const unsigned char *sha1)
 	return buffer;
 }
 
+char *oid_to_hex_r(char *buffer, const struct object_id *oid)
+{
+	return sha1_to_hex_r(buffer, oid->hash);
+}
+
 char *sha1_to_hex(const unsigned char *sha1)
 {
 	static int bufno;