Oldurl

If an article has an Oldurl defined in it's metadata then an entry to redirect from that url to the articles pelican generated url is added to a list of such redirects.

This list is then read by the .htaccess template when the site is built, which instructs apache to do the redirect.

This was mostly for when the site transitioned to being a statically generated Pelican site in 2015. The old site in its entirety was copied to /old/. This redirection means that pre 2015 articles that have been updated and converted (to markdown) are accessible from their old urls. If they haven't been converted then their is a different redirect rule that inserts /old/ into the url. So you always see the article, preferentially the new article if it exists.