sitemap generation does not support incremental builds

[2bndy5]

The sphinx_immaterial.postprocess_html extension handles the generation of a sitemap, but it does not include unchanged pages' data from a previous builds. I believe this extension was inherited from sphinx-material theme.

This behavior has been adequate because docs are typically deployed from a fresh build.
However, this lacking implementation may impact versioned docs using the version selector.

Tip

For passersby, the sitemap is automatically generated when html_theme_options["site_url"] is configured.