+
+ /*
+ * We've found the first non-matching character in the directory
+ * paths. That means the current characters we were looking at
+ * were part of the first non-matching subdir name going back from
+ * the end of the strings. Get the whole name by advancing both
+ * end_of_old and end_of_new to the NEXT '/' character. That will
+ * represent the entire directory rename.
+ *
+ * The reason for the increment is cases like
+ * a/b/star/foo/whatever.c -> a/b/tar/foo/random.c
+ * After dropping the basename and going back to the first
+ * non-matching character, we're now comparing:
+ * a/b/s and a/b/
+ * and we want to be comparing:
+ * a/b/star/ and a/b/tar/
+ * but without the pre-increment, the one on the right would stay
+ * a/b/.
+ */
+ end_of_old = strchr(++end_of_old, '/');
+ end_of_new = strchr(++end_of_new, '/');
+
+ /* Copy the old and new directories into *old_dir and *new_dir. */
+ *old_dir = xstrndup(old_path, end_of_old - old_path);
+ *new_dir = xstrndup(new_path, end_of_new - new_path);