discourse/app/views/robots_txt/index.erb

# See http://www.robotstxt.org/wc/norobots.html for documentation on how to use the robots.txt file
#
User-agent: *
Disallow: /auth/cas
Disallow: /auth/facebook/callback
Disallow: /auth/twitter/callback
Disallow: /auth/google/callback
Disallow: /auth/yahoo/callback
Disallow: /auth/github/callback
Disallow: /auth/cas/callback
Disallow: /assets/browser-update*.js
Disallow: /users/
Disallow: /badges/