Feature-Request: make parent link customizable

[DirkSchmitt]

The --parent-gal option will create links to ../index.html.
In the use case that the upper directory is exposed as directory listing without an index.html page this may fail.

IMHO it would be a good idea to make the link goal customizable.

[DirkSchmitt]

Currently I work around this issue with: sed -e 's;href="../index.html";href="..";g' --in-place index.html