Deprecate autoload_files

src/Command/CommandHelper.php

@@ -298,7 +298,26 @@ public static function begin(
 			throw new \PHPStan\Command\InceptionNotSuccessfulException();
 		}
 
-		foreach ($container->getParameter('autoload_files') as $parameterAutoloadFile) {
+		$autoloadFiles = $container->getParameter('autoload_files');
+		if (count($autoloadFiles) > 0) {
+			$errorOutput->writeLineFormatted('⚠️  You\'re using a deprecated config option <fg=cyan>autoload_files</>. ⚠️️');
+			$errorOutput->writeLineFormatted('');
+			$errorOutput->writeLineFormatted('You might not need it anymore - try removing it from your');
+			$errorOutput->writeLineFormatted('configuration file and run PHPStan again.');
+			$errorOutput->writeLineFormatted('');
+			$errorOutput->writeLineFormatted('If the analysis fails, there are now two distinct options');
+			$errorOutput->writeLineFormatted('to choose from to replace <fg=cyan>autoload_files</>:');
+			$errorOutput->writeLineFormatted('1) <fg=cyan>scanFiles</> - PHPStan will scan those for classes and functions');
+			$errorOutput->writeLineFormatted('   definitions. PHPStan will not execute those files.');
+			$errorOutput->writeLineFormatted('2) <fg=cyan>bootstrapFiles</> - PHPStan will execute these files to prepare');
+			$errorOutput->writeLineFormatted('   the PHP runtime environment for the analysis.');
+			$errorOutput->writeLineFormatted('');
+			$errorOutput->writeLineFormatted('Read more about this in PHPStan\'s documentation:');
+			$errorOutput->writeLineFormatted('https://phpstan.org/user-guide/discovering-symbols');
+			$errorOutput->writeLineFormatted('');
+		}
+
+		foreach ($autoloadFiles as $parameterAutoloadFile) {
 			if (!file_exists($parameterAutoloadFile)) {
 				$errorOutput->writeLineFormatted(sprintf('Autoload file %s does not exist.', $parameterAutoloadFile));
 				throw new \PHPStan\Command\InceptionNotSuccessfulException();