title: How to update an existing .po file with a newly generated .pot file?
body: <p>Cake version is 2.x. I have extracted all the texts inside <code>__</code> function with <code>./Console/cake i18n extract</code> command, moved the <code>default.pot</code> file into <code>app/Locale/[iso3]/LC_MESSAGES/default.po</code> and translated it to corresponding language. Everything is working fine.</p>
  
  <p>After some time I have added some new functionality into the site and I need to add those messages into the <code>po</code> file. However if I use the same command it will create a new pot and I have to either manually merge them or replace with new po file and copy/paste the translations - both are too much manual work, because I have a few thousand lines of text. </p>
  
  <p>Is there any way to tell cake update my <code>po</code> file adding only messages that does not exist in there ?</p>
  
  <p>Thanks</p>