Rewriting pages to re-rendered snapshots

[rootberry]

I have a very Javascript heavy website which is being served by nginx. It
all works great, except Google is having trouble indexing me. I've made
pre-rendered snapshots of all my pages using Phantomjs and these are stored
in /snapshots (relative to my website's root).

I've been using this rewrite rule to detect the Google bot and serve it a
snapshot:

        location / {

                if ($args ~ "_escaped_fragment_=") {
                        rewrite ^/(.*)$ /snapshots/$1.html break;
                }

        }

It works for all pages apart from the homepage. In the snapshots directory,
the home page is called index.html, however the Google bot requests
http://mysite.com/?_escaped_fragment_= when it wants the home page, which
makes this rewrite rule return a 404.

How can I adapt this rule to return the index.html snapshot when / is
requested?

Thanks!

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,240435,240435#msg-240435