assert_redirected_to is currently a pretty complicated beast at
present, so I thought I'd spend some time trying out what's involved
in changing it to be a two line method.

The results are at

One casualty of this approach will be the 'pretty diffs'. I've almost
never found them interesting, but I'm wondering if anyone else here
has strong opinions on their utility.

So I'd appreciate it if you could apply the patch to your own
applications and let me know whether or not it breaks any assertions.
If something breaks, please provide as much detail as possible about
the controller structure.

Assuming it doesn't break anything, and the pretty diffs aren't sorely
missed, I'd like to get this into trunk sooner rather than later.