Use branch-specific cache file for PHP-CS-Fixer

Author: sebastianbergmann

.gitignore

@@ -14,7 +14,7 @@
 
 # PHP-CS-Fixer
 /.php-cs-fixer.php
-/.php-cs-fixer.cache
+/.php-cs-fixer.cache*
 
 # Psalm
 /.psalm/cache

.php-cs-fixer.dist.php

@@ -341,4 +341,10 @@
         'whitespace_after_comma_in_array' => true,
     ]);
 
+$branch = @trim((string) @shell_exec('git rev-parse --abbrev-ref HEAD'));
+
+if (!empty($branch)) {
+    $config->setCacheFile(__DIR__ . '/.php-cs-fixer.cache.' . $branch);
+}
+
 return $config;