[Process] Fix escaping /X arguments on Windows

Author: nicolas-grekas

Process.php

@@ -1638,7 +1638,7 @@ private function escapeArgument(?string $argument): string
         if (str_contains($argument, "\0")) {
             $argument = str_replace("\0", '?', $argument);
         }
-        if (!preg_match('/[\/()%!^"<>&|\s]/', $argument)) {
+        if (!preg_match('/[()%!^"<>&|\s]/', $argument)) {
             return $argument;
         }
         $argument = preg_replace('/(\\\\+)$/', '$1$1', $argument);

Tests/ProcessTest.php

@@ -1424,7 +1424,12 @@ public function testGetCommandLine()
     {
         $p = new Process(['/usr/bin/php']);
 
-        $expected = '\\' === \DIRECTORY_SEPARATOR ? '"/usr/bin/php"' : "'/usr/bin/php'";
+        $expected = '\\' === \DIRECTORY_SEPARATOR ? '/usr/bin/php' : "'/usr/bin/php'";
+        $this->assertSame($expected, $p->getCommandLine());
+
+        $p = new Process(['cd', '/d']);
+
+        $expected = '\\' === \DIRECTORY_SEPARATOR ? 'cd /d' : "'cd' '/d'";
         $this->assertSame($expected, $p->getCommandLine());
     }