Add documentation for new postgres initdb logic

Author: tianon

postgres/content.md

@@ -45,7 +45,7 @@ This optional environment variable can be used to define another location - like
 
 # How to extend this image
 
-If you would like to do additional initialization in an image derived from this one, add a `*.sh` script under `/docker-entrypoint-initdb.d` (creating the directory if necessary). After the entrypoint calls `initdb` to create the default `postgres` user and database, it will source any `*.sh` script found in that directory to do further initialization before starting the service. If you need to execute SQL commands as part of your initialization, the use of Postgres'' [single user mode](http://www.postgresql.org/docs/9.3/static/app-postgres.html#AEN90580) is highly recommended.
+If you would like to do additional initialization in an image derived from this one, add a `*.sql` or `*.sh` script under `/docker-entrypoint-initdb.d` (creating the directory if necessary). After the entrypoint calls `initdb` to create the default `postgres` user and database, it will run any `*.sql` files and source any `*.sh` script found in that directory to do further initialization before starting the service.
 
 You can also extend the image with a simple `Dockerfile` to set the locale. The following example will set the default locale to `de_DE.utf8`: