I am doing something very simple wrong. I'm trying to prepare an ordinary patch file, so I can reapply some changes:

$ git diff > before
$ git diff something_here > save.patch
$ git checkout . 
$ patch < save.patch
$ git diff > after
$ diff before after
$

With something_here blank it almost works, but the file names aren't right. I think I'm just I'm missing some option.

In real life, I am going to do a merge after the checkout, so the patch might fail there, but you see what I'm getting at.