The help pages are currently written in ducktype. The files are stored in help/C/duck and the corresponding .page-files can be generated via make -C help/C/. Afterwards, you can preview the generated help pages via yelp help/C/index.page. The generated .page-files have to be committed to the repository as well. The ducktype program required for running make is probably packaged in you distro and is also availabe on GitHub.