Fix 'gcc -Wextra -Wno-unused-parameter'.

src/util.c

@@ -130,7 +130,7 @@ char *resolve_tilde(const char *path) {
         char *head, *tail, *result;
 
         tail = strchr(path, '/');
-        head = strndup(path, tail ? tail - path : strlen(path));
+        head = strndup(path, tail ? (size_t)(tail - path) : strlen(path));
 
         int res = glob(head, GLOB_TILDE, NULL, &globbuf);
         free(head);