title: PHPStan, exclude all and specify files to check
body: <p>Im trying to setup PHPStan on a older, bigger, codebase. How could i exclude everything and than maybe by config define what to analyse.</p>
  
  <p>I have thought about using a separate folder for it, but that would mean constantly moving files which might lead to breaking of the code. So i am hoping to exclude everything and then adding files to the analysers per file.</p>
  
  <p>At this moment the only solution i was able to find is defining a script in <code>composer.json</code>
  <code><pre>
    "scripts": {
      "phpstan": "./vendor/bin/phpstan analyse --memory-limit=1G --no-progress --level 1 `cat phpstan_analyse_files`"
    }
  </pre></code></p>
  
  <p>And keeping a list of files to analyise in the file <code>phpstan_analyse_files</code></p>