[dspillett]

> When using static site generators, it's not even possible to do 301 redirects (you would have to ugly slow JS version).

That isn't always true, depending on your choice of web server. You can use mod_rewrite rules in Apache's .htaccess files so if your generator is aware of previous URLs for given content it could generate these to 30x redirect visitors and search bots to the new right place.

Off the top of my head I'm not aware of a tool that does this, but it is certainly possible. It would need to track the old content/layout so you'd need the content in a DB with history tracking (or a source control system) or the tool could leave information about previous generations on each run for later reading. Or it could simply rely on the user defining redirect links for it to include in the generated site.

Of course if you are using a static site generator for maximum efficiency you probably aren't using Apache with .htaccess processing enabled! I suppose a generator could also generate a config fragment for nginx/other similarly though that would not be useful if you are publishing via a web server where you do not have appropriately privileged access to make changes to that.