fix(Finder): ExcludeDirectoryFilterIterator relative to "root" if /

Fixes #28158
Fixes #47431

Related: #26396
Related: #9158
Related: #28410

src/Symfony/Component/Finder/Iterator/ExcludeDirectoryFilterIterator.php

@@ -30,6 +30,7 @@ class ExcludeDirectoryFilterIterator extends \FilterIterator implements \Recursi
     /** @var array<string, true> */
     private array $excludedDirs = [];
     private ?string $excludedPattern = null;
+    private ?string $excludedPatternAbsolute = null;
     /** @var list<callable(SplFileInfo):bool> */
     private array $pruneFilters = [];
 
@@ -42,6 +43,7 @@ public function __construct(\Iterator $iterator, array $directories)
         $this->iterator = $iterator;
         $this->isRecursive = $iterator instanceof \RecursiveIterator;
         $patterns = [];
+        $patternsAbsolute = [];
         foreach ($directories as $directory) {
             if (!\is_string($directory)) {
                 if (!\is_callable($directory)) {
@@ -54,7 +56,13 @@ public function __construct(\Iterator $iterator, array $directories)
             }
 
             $directory = rtrim($directory, '/');
-            if (!$this->isRecursive || str_contains($directory, '/')) {
+            $slashPos = strpos($directory, '/');
+            if (false !== $slashPos && \strlen($directory) - 1 !== $slashPos) {
+                if (0 === $slashPos) {
+                    $directory = substr($directory, 1);
+                }
+                $patternsAbsolute[] = preg_quote($directory, '#');
+            } elseif (!$this->isRecursive || str_contains($directory, '/')) {
                 $patterns[] = preg_quote($directory, '#');
             } else {
                 $this->excludedDirs[$directory] = true;
@@ -64,6 +72,10 @@ public function __construct(\Iterator $iterator, array $directories)
             $this->excludedPattern = '#(?:^|/)(?:'.implode('|', $patterns).')(?:/|$)#';
         }
 
+        if ($patternsAbsolute) {
+            $this->excludedPatternAbsolute = '#^('.implode('|', $patternsAbsolute).')$#';
+        }
+
         parent::__construct($iterator);
     }
 
@@ -76,11 +88,15 @@ public function accept(): bool
             return false;
         }
 
-        if ($this->excludedPattern) {
+        if ($this->excludedPattern || $this->excludedPatternAbsolute) {
             $path = $this->isDir() ? $this->current()->getRelativePathname() : $this->current()->getRelativePath();
             $path = str_replace('\\', '/', $path);
-
-            return !preg_match($this->excludedPattern, $path);
+        }
+        if ($this->excludedPattern && preg_match($this->excludedPattern, $path)) {
+            return false;
+        }
+        if ($this->excludedPatternAbsolute && preg_match($this->excludedPatternAbsolute, $path)) {
+            return false;
         }
 
         if ($this->pruneFilters && $this->hasChildren()) {