Mention Unicorn on a domain socket as an exception

config.yml.example

@@ -4,7 +4,8 @@ user: git
 # Url to gitlab instance. Used for api calls. Should end with a slash.
 # Default: http://localhost:8080/
 # You only have to change the default if you have configured Unicorn
-# to listen on a custom port.
+# to listen on a custom port, or if you have configured Unicorn to
+# only listen on a Unix domain socket.
 gitlab_url: "http://localhost:8080/"
 
 http_settings: