Login flow redirects to landing page instead of previous page

I noticed today that the login process seems to lose track of where the user is coming from:

- Visit a ticket page while not logged in
- Click "Login" in the navigation
- Choose "log in with github"

Once login is successful, I find myself redirected to the root page `/` and not the ticket page that I was browsing when I clicked the "Login" link.

It's slightly annoying and I think it should be fixable by passing the right redirection URL to the login page (via a GET parameter).