There are multiple pieces of documentation that are processed and used differently.

The rpm.org web page is created from its own GitHub repository.

The man pages in man/ are Markdown documents. They are rendered to the man page format during build. These pre-rendered pages are also shipped with the (release) tarball. That way building rpm from the tarball does not require the pandoc as long as the man pages are unchanged.

The man pages are also rendered to HTML together with the Reference Manual (see below).

The API reference is rendered with Doxygen. The content is almost exclusively created from the RPM sources and the doc strings there in. The rendered HTML is shipped with the release tarball to be able to build RPM from that without Doxygen.

The reference manual in the manual/ dir is an GitHub Pages site. It is rendered automatically when pushed into the master branch in the GitHub repository. It is available online on its own URL but is intended to be used as part of the RPM.org website were it is linked from the Documentation page

The Reference Manual is currently not shipped in rendered form in the tarball.

To render it locally one can follow this article and render it with Jekyll with the use of the github-pages gem.