By being written by people smarter than me
The main issue with Zola rebuilds is that we currently do not inspect the AST of the templates and the global functions means that any content can be anywhere on the site: for example you might have a sidebar shown on every page containing the last 5 articles. This means that every single page needs to be rewritten but we don’t know about it in Zola since it all lives in the templates. That’s only one example, there are a few other tricky ones: changing date/order of a page, changing
transparent etc. Those ones we can do the diff but because of the global functions we don’t know if we actually need to render more than the minimum.