./console exp:exphelp --help
./console exp:help --help
php bin/php/exphelp.php --help

The help system: the index of the documentation, its search and its link check

./console exp:help index                     build the index (if it is not current) and describe it
./console exp:help index --rebuild           build it again, whatever is cached
./console exp:help index --list              one line per page: id, type, category, audiences, title
./console exp:help index --no-images         without fetching the pages' external images
./console exp:help search "clear cache"      search the pages (--audience, --category, --type, --limit)
./console exp:help show guides/caches.md     the metadata and headings of one page
./console exp:help check                     check the links and images of every page (--below=guides/)
./console exp:help pdf help/searching.md      the page as a PDF file (--out=file.pdf, --base-url=https://host)
./console exp:help maps --language=ger-de    check doc/ger-de/.paths.json and .dirnames.json; --fix writes the
                                             union of both sides of a git conflict (and of --paths=, --dirnames=)

Only git-tracked files below doc/ (and the doc/ of the extensions in exphelp.ini ExtensionDocDirs[]) are
pages; nothing is changed except the cache in var/<site>/cache/exphelp. --json prints one JSON document.
index builds the index of every language of exphelp.ini [DocLanguages] (doc/eng-us/, doc/ger-de/ ...);
--language=ger-de limits it to one, and makes search, show, check and pdf read that language.
index also stores a copy of every https image a page shows (README.md's screenshots) in the cache's
images/, served by exphelp/image, so the admin's Content Security Policy allows them.
Exit code: 0 fine, 1 check found errors (with --strict also warnings) or nothing was found, 2 error.