Meson uses itself and hotdoc for generating documentation.
Minimum required version of hotdoc is 0.8.9.
Instructions on how to install hotdoc are here.
From the Meson repository root dir:
$ cd docs/ $ meson setup built_docs/ $ ninja -C built_docs/
Now you should be able to open the documentation locally
Meson uses the git-upload hotdoc plugin which basically removes the html pages and replaces with the new content.
You can simply run:
$ ninja -C built_docs/ upload