A permalink_fu improvement: allow modification of permalinks and send HTTP redirects on-the-fly

Another spin-off from the www.visitacsa.it website: a permalink_fu improvement that allows dynamic permalinks. I know it is an oxymoron, because permalinks should be .. well .. permanent! And because search engines index them, they should never change. But what happens when you publish something, your permalink is generated with permalink_fu using the title of your post, and after a couple of days you want to change the title, and the permalink under which the post is accessible as well?

Following the specification, your app should send out a 301 moved permanently HTTP status when accessing the old permalink and redirect the client to the new Uniform Resource Locator. That’s quite the same thing what my modification to permalink_fu does: whenever your post attributes are changed, the former and new permalinks are saved to the database, and you can enable your controller to generate 302 moved temporarily redirects when needed. In other words, it checks whether the requested URL is an old permalink, and automagically redirects the client to the new one.

Everything is done behind the scenes, and the plugin has also got nifty rake tasks to set up the Redirect model and associated migrations. And you can change its name, of course! :)

The 302 code was chosen because the 301 permanent status code has quite disruptive effects on search engines, but more discussion is welcome.

Have a look over my repository at github, read the README that contains the documentation of the added features, and check out the code!