+/* Call this with EITHER (1) "file, NULL, 0" to chdir() to the file's
+ * F_PATHNAME(), or (2) "NULL, dir, dirlen" to chdir() to the supplied dir,
+ * with dir == NULL taken to be the starting directory, and dirlen < 0
+ * indicating that strdup(dir) should be called and then the -dirlen length
+ * value checked to ensure that it is not daemon-excluded. */
+int change_pathname(struct file_struct *file, const char *dir, int dirlen)