builtin-rerere: fix a small leak

The data read from MERGE_RR file is kept in path-list by hanging textual
40-byte conflict signature to path of the blob that contains the
conflict.  The signature is strdup'ed twice, and the second copy is given
to the path-list, leaking the first copy.
Signed-off-by: NJunio C Hamano <junio@pobox.com>
Acked-by: NJohannes Schindelin <Johannes.Schindelin@gmx.de>

builtin-rerere.c

@@ -43,7 +43,7 @@ static void read_rr(struct path_list *rr)
 			; /* do nothing */
 		if (i == sizeof(buf))
 			die("filename too long");
-		path_list_insert(buf, rr)->util = xstrdup(name);
+		path_list_insert(buf, rr)->util = name;
 	}
 	fclose(in);
 }