Find out if post was just updated on post edit screen

I figured it out by looking in WP Core. When you update a post it actually takes you back to the edit posts screen (post.php) with a GET parameter of message=1. And then it erases that parameter from the url with javascript quickly. So you can find out if posts were uploaded in a plugin by checking:

if ($_GET['message'] == 1) {
  // do something because the post was just updated
}