title: Autocommit off, BEGIN and warning about transaction in progress
body: <p>I like to have this in my <code>~/.psqlrc</code>:</p>
  
  <pre><code>\set autocommit off
  </code></pre>
  
  <p>I also like this at the top of my <code>filename.sql</code> scripts:</p>
  
  <pre><code>BEGIN;
  </code></pre>
  
  <p>...in case those scripts are run by others who uses autocommit.</p>
  
  <p>However, this emits warnings:</p>
  
  <pre><code>WARNING:  there is already a transaction in progress
  </code></pre>
  
  <p>How can I turn off those annoying warnings? Is there some sort of <code>BEGIN IF NOT ALREADY BEGUN</code> command?</p>