Merge branch '3.4' into 4.3

* 3.4:
  [Validator] Allow underscore character "_" in URL username and password
  [SecurityBundle] Passwords are not encoded when algorithm set to \"true\"
  do not validate passwords when the hash is null
  [DI] Fix making the container path-independent when the app is in /app
  Allow copy instead of symlink for ./link script
  [FrameworkBundle] resolve service locators in `debug:*` commands
  bumped Symfony version to 3.4.37
  updated VERSION for 3.4.36
  update CONTRIBUTORS for 3.4.36
  updated CHANGELOG for 3.4.36

Author: xabbuh

Dumper/PhpDumper.php

@@ -194,14 +194,14 @@ public function dump(array $options = [])
         if (!empty($options['file']) && is_dir($dir = \dirname($options['file']))) {
             // Build a regexp where the first root dirs are mandatory,
             // but every other sub-dir is optional up to the full path in $dir
-            // Mandate at least 2 root dirs and not more that 5 optional dirs.
+            // Mandate at least 1 root dir and not more than 5 optional dirs.
 
             $dir = explode(\DIRECTORY_SEPARATOR, realpath($dir));
             $i = \count($dir);
 
-            if (3 <= $i) {
+            if (2 + (int) ('\\' === \DIRECTORY_SEPARATOR) <= $i) {
                 $regex = '';
-                $lastOptionalDir = $i > 8 ? $i - 5 : 3;
+                $lastOptionalDir = $i > 8 ? $i - 5 : (2 + (int) ('\\' === \DIRECTORY_SEPARATOR));
                 $this->targetDirMaxMatches = $i - $lastOptionalDir;
 
                 while (--$i >= $lastOptionalDir) {