I released a plugin that will handle the multi-module project scenario with github pages. It is a matter of setting the following dependency on maven-site-plugin
<plugin>
<artifactId>maven-site-plugin</artifactId>
<version>3.3</version>
<dependencies>
<dependency>
<groupId>net.trajano.wagon</groupId>
<artifactId>wagon-git</artifactId>
<version>1.0.0</version>
</dependency>
<dependencies>
</plugin>
The following is the multi-module example https://github.com/trajano/app/tree/wagon-git-example which can be seen at http://site.trajano.net/app/