diff --git a/core/update.php b/core/update.php
index 52cf3d0..7150e04 100644
--- a/core/update.php
+++ b/core/update.php
@@ -14,8 +14,14 @@
  * back to its original state!
  */
 
-use Symfony\Component\HttpFoundation\Request;
-use Symfony\Component\HttpFoundation\Response;
+// Exit early if an incompatible PHP version would cause fatal errors.
+// The minimum version is specified explicitly, as DRUPAL_MINIMUM_PHP is not
+// yet available. It is defined in bootstrap.inc, but it is not possible to
+// load that file yet as it would cause a fatal error on older versions of PHP.
+if (version_compare(PHP_VERSION, '5.3.3') < 0) {
+  print 'Your PHP installation is too old. Drupal requires at least PHP 5.3.3. See the <a href="http://drupal.org/requirements">system requirements</a> page for more information.';
+  exit;
+}
 
 // Change the directory to the Drupal root.
 chdir('..');
@@ -25,14 +31,8 @@ chdir('..');
  */
 define('DRUPAL_ROOT', getcwd());
 
-// Exit early if an incompatible PHP version would cause fatal errors.
-// The minimum version is specified explicitly, as DRUPAL_MINIMUM_PHP is not
-// yet available. It is defined in bootstrap.inc, but it is not possible to
-// load that file yet as it would cause a fatal error on older versions of PHP.
-if (version_compare(PHP_VERSION, '5.3.3') < 0) {
-  print 'Your PHP installation is too old. Drupal requires at least PHP 5.3.3. See the <a href="http://drupal.org/requirements">system requirements</a> page for more information.';
-  exit;
-}
+// Start the update.
+require_once DRUPAL_ROOT . '/core/includes/update.core.inc';
 
 /**
  * Global flag indicating that update.php is being run.
@@ -46,476 +46,4 @@ if (version_compare(PHP_VERSION, '5.3.3') < 0) {
  */
 define('MAINTENANCE_MODE', 'update');
 
-/**
- * Renders form with a list of available database updates.
- */
-function update_selection_page() {
-  drupal_set_title('Drupal database update');
-  $elements = drupal_get_form('update_script_selection_form');
-  $output = drupal_render($elements);
-
-  update_task_list('select');
-
-  return $output;
-}
-
-/**
- * Form constructor for the list of available database module updates.
- */
-function update_script_selection_form($form, &$form_state) {
-  $count = 0;
-  $incompatible_count = 0;
-  $form['start'] = array(
-    '#tree' => TRUE,
-    '#type' => 'fieldset',
-    '#collapsed' => TRUE,
-    '#collapsible' => TRUE,
-  );
-
-  // Ensure system.module's updates appear first.
-  $form['start']['system'] = array();
-
-  $updates = update_get_update_list();
-  $starting_updates = array();
-  $incompatible_updates_exist = FALSE;
-  foreach ($updates as $module => $update) {
-    if (!isset($update['start'])) {
-      $form['start'][$module] = array(
-        '#type' => 'item',
-        '#title' => $module . ' module',
-        '#markup'  => $update['warning'],
-        '#prefix' => '<div class="messages warning">',
-        '#suffix' => '</div>',
-      );
-      $incompatible_updates_exist = TRUE;
-      continue;
-    }
-    if (!empty($update['pending'])) {
-      $starting_updates[$module] = $update['start'];
-      $form['start'][$module] = array(
-        '#type' => 'hidden',
-        '#value' => $update['start'],
-      );
-      $form['start'][$module . '_updates'] = array(
-        '#theme' => 'item_list',
-        '#items' => $update['pending'],
-        '#title' => $module . ' module',
-      );
-    }
-    if (isset($update['pending'])) {
-      $count = $count + count($update['pending']);
-    }
-  }
-
-  // Find and label any incompatible updates.
-  foreach (update_resolve_dependencies($starting_updates) as $function => $data) {
-    if (!$data['allowed']) {
-      $incompatible_updates_exist = TRUE;
-      $incompatible_count++;
-      $module_update_key = $data['module'] . '_updates';
-      if (isset($form['start'][$module_update_key]['#items'][$data['number']])) {
-        $text = $data['missing_dependencies'] ? 'This update will been skipped due to the following missing dependencies: <em>' . implode(', ', $data['missing_dependencies']) . '</em>' : "This update will be skipped due to an error in the module's code.";
-        $form['start'][$module_update_key]['#items'][$data['number']] .= '<div class="warning">' . $text . '</div>';
-      }
-      // Move the module containing this update to the top of the list.
-      $form['start'] = array($module_update_key => $form['start'][$module_update_key]) + $form['start'];
-    }
-  }
-
-  // Warn the user if any updates were incompatible.
-  if ($incompatible_updates_exist) {
-    drupal_set_message('Some of the pending updates cannot be applied because their dependencies were not met.', 'warning');
-  }
-
-  if (empty($count)) {
-    drupal_set_message(t('No pending updates.'));
-    unset($form);
-    $form['links'] = array(
-      '#theme' => 'links',
-      '#links' => update_helpful_links(),
-    );
-
-    // No updates to run, so caches won't get flushed later.  Clear them now.
-    drupal_flush_all_caches();
-  }
-  else {
-    $form['help'] = array(
-      '#markup' => '<p>The version of Drupal you are updating from has been automatically detected.</p>',
-      '#weight' => -5,
-    );
-    if ($incompatible_count) {
-      $form['start']['#title'] = format_plural(
-        $count,
-        '1 pending update (@number_applied to be applied, @number_incompatible skipped)',
-        '@count pending updates (@number_applied to be applied, @number_incompatible skipped)',
-        array('@number_applied' => $count - $incompatible_count, '@number_incompatible' => $incompatible_count)
-      );
-    }
-    else {
-      $form['start']['#title'] = format_plural($count, '1 pending update', '@count pending updates');
-    }
-    $form['actions'] = array('#type' => 'actions');
-    $form['actions']['submit'] = array(
-      '#type' => 'submit',
-      '#value' => 'Apply pending updates',
-    );
-  }
-  return $form;
-}
-
-/**
- * Provides links to the homepage and administration pages.
- */
-function update_helpful_links() {
-  $links['front'] = array(
-    'title' => t('Front page'),
-    'href' => '<front>',
-  );
-  if (user_access('access administration pages')) {
-    $links['admin-pages'] = array(
-      'title' => t('Administration pages'),
-      'href' => 'admin',
-    );
-  }
-  return $links;
-}
-
-/**
- * Displays results of the update script with any accompanying errors.
- */
-function update_results_page() {
-  drupal_set_title('Drupal database update');
-
-  update_task_list();
-  // Report end result.
-  if (module_exists('dblog') && user_access('access site reports')) {
-    $log_message = ' All errors have been <a href="' . base_path() . '?q=admin/reports/dblog">logged</a>.';
-  }
-  else {
-    $log_message = ' All errors have been logged.';
-  }
-
-  if ($_SESSION['update_success']) {
-    $output = '<p>Updates were attempted. If you see no failures below, you may proceed happily back to your <a href="' . base_path() . '">site</a>. Otherwise, you may need to update your database manually.' . $log_message . '</p>';
-  }
-  else {
-    list($module, $version) = array_pop(reset($_SESSION['updates_remaining']));
-    $output = '<p class="error">The update process was aborted prematurely while running <strong>update #' . $version . ' in ' . $module . '.module</strong>.' . $log_message;
-    if (module_exists('dblog')) {
-      $output .= ' You may need to check the <code>watchdog</code> database table manually.';
-    }
-    $output .= '</p>';
-  }
-
-  if (!empty($GLOBALS['update_free_access'])) {
-    $output .= "<p><strong>Reminder: don't forget to set the <code>\$update_free_access</code> value in your <code>settings.php</code> file back to <code>FALSE</code>.</strong></p>";
-  }
-
-  $output .= theme('links', array('links' => update_helpful_links()));
-
-  // Output a list of queries executed.
-  if (!empty($_SESSION['update_results'])) {
-    $all_messages = '';
-    foreach ($_SESSION['update_results'] as $module => $updates) {
-      if ($module != '#abort') {
-        $module_has_message = FALSE;
-        $query_messages = '';
-        foreach ($updates as $number => $queries) {
-          $messages = array();
-          foreach ($queries as $query) {
-            // If there is no message for this update, don't show anything.
-            if (empty($query['query'])) {
-              continue;
-            }
-
-            if ($query['success']) {
-              $messages[] = '<li class="success">' . $query['query'] . '</li>';
-            }
-            else {
-              $messages[] = '<li class="failure"><strong>Failed:</strong> ' . $query['query'] . '</li>';
-            }
-          }
-
-          if ($messages) {
-            $module_has_message = TRUE;
-            $query_messages .= '<h4>Update #' . $number . "</h4>\n";
-            $query_messages .= '<ul>' . implode("\n", $messages) . "</ul>\n";
-          }
-        }
-
-        // If there were any messages in the queries then prefix them with the
-        // module name and add it to the global message list.
-        if ($module_has_message) {
-          $all_messages .= '<h3>' . $module . " module</h3>\n" . $query_messages;
-        }
-      }
-    }
-    if ($all_messages) {
-      $output .= '<div id="update-results"><h2>The following updates returned messages</h2>';
-      $output .= $all_messages;
-      $output .= '</div>';
-    }
-  }
-  unset($_SESSION['update_results']);
-  unset($_SESSION['update_success']);
-
-  return $output;
-}
-
-function update_info_page() {
-  // Change query-strings on css/js files to enforce reload for all users.
-  _drupal_flush_css_js();
-  // Flush the cache of all data for the update status module.
-  if (db_table_exists('cache_update')) {
-    cache('update')->flush();
-  }
-
-  update_task_list('info');
-  drupal_set_title('Drupal database update');
-  $token = drupal_get_token('update');
-  $output = '<p>Use this utility to update your database whenever a new release of Drupal or a module is installed.</p><p>For more detailed information, see the <a href="http://drupal.org/upgrade">upgrading handbook</a>. If you are unsure what these terms mean you should probably contact your hosting provider.</p>';
-  $output .= "<ol>\n";
-  $output .= "<li><strong>Back up your database</strong>. This process will change your database values and in case of emergency you may need to revert to a backup.</li>\n";
-  $output .= "<li><strong>Back up your code</strong>. Hint: when backing up module code, do not leave that backup in the 'modules' or 'sites/*/modules' directories as this may confuse Drupal's auto-discovery mechanism.</li>\n";
-  $output .= '<li>Put your site into <a href="' . base_path() . '?q=admin/config/development/maintenance">maintenance mode</a>.</li>' . "\n";
-  $output .= "<li>Install your new files in the appropriate location, as described in the handbook.</li>\n";
-  $output .= "</ol>\n";
-  $output .= "<p>When you have performed the steps above, you may proceed.</p>\n";
-  $form_action = check_url(drupal_current_script_url(array('op' => 'selection', 'token' => $token)));
-  $output .= '<form method="post" action="' . $form_action . '"><p><input type="submit" value="Continue" class="form-submit" /></p></form>';
-  $output .= "\n";
-  return $output;
-}
-
-function update_access_denied_page() {
-  drupal_add_http_header('Status', '403 Forbidden');
-  watchdog('access denied', 'update.php', array(), WATCHDOG_WARNING);
-  drupal_set_title('Access denied');
-  return '<p>Access denied. You are not authorized to access this page. Log in using either an account with the <em>administer software updates</em> permission or the site maintenance account (the account you created during installation). If you cannot log in, you will have to edit <code>settings.php</code> to bypass this access check. To do this:</p>
-<ol>
- <li>With a text editor find the settings.php file on your system. From the main Drupal directory that you installed all the files into, go to <code>sites/your_site_name</code> if such directory exists, or else to <code>sites/default</code> which applies otherwise.</li>
- <li>There is a line inside your settings.php file that says <code>$update_free_access = FALSE;</code>. Change it to <code>$update_free_access = TRUE;</code>.</li>
- <li>As soon as the update.php script is done, you must change the settings.php file back to its original form with <code>$update_free_access = FALSE;</code>.</li>
- <li>To avoid having this problem in the future, remember to log in to your website using either an account with the <em>administer software updates</em> permission or the site maintenance account (the account you created during installation) before you backup your database at the beginning of the update process.</li>
-</ol>';
-}
-
-/**
- * Determines if the current user is allowed to run update.php.
- *
- * @return
- *   TRUE if the current user should be granted access, or FALSE otherwise.
- */
-function update_access_allowed() {
-  global $update_free_access, $user;
-
-  // Allow the global variable in settings.php to override the access check.
-  if (!empty($update_free_access)) {
-    return TRUE;
-  }
-  // Calls to user_access() might fail during the Drupal 6 to 7 update process,
-  // so we fall back on requiring that the user be logged in as user #1.
-  try {
-    require_once DRUPAL_ROOT . '/' . drupal_get_path('module', 'user') . '/user.module';
-    return user_access('administer software updates');
-  }
-  catch (Exception $e) {
-    return ($user->uid == 1);
-  }
-}
-
-/**
- * Adds the update task list to the current page.
- */
-function update_task_list($active = NULL) {
-  // Default list of tasks.
-  $tasks = array(
-    'requirements' => 'Verify requirements',
-    'info' => 'Overview',
-    'select' => 'Review updates',
-    'run' => 'Run updates',
-    'finished' => 'Review log',
-  );
-
-  drupal_add_region_content('sidebar_first', theme('task_list', array('items' => $tasks, 'active' => $active)));
-}
-
-/**
- * Returns and stores extra requirements that apply during the update process.
- */
-function update_extra_requirements($requirements = NULL) {
-  static $extra_requirements = array();
-  if (isset($requirements)) {
-    $extra_requirements += $requirements;
-  }
-  return $extra_requirements;
-}
-
-/**
- * Checks update requirements and reports errors and (optionally) warnings.
- *
- * @param $skip_warnings
- *   (optional) If set to TRUE, requirement warnings will be ignored, and a
- *   report will only be issued if there are requirement errors. Defaults to
- *   FALSE.
- */
-function update_check_requirements($skip_warnings = FALSE) {
-  // Check requirements of all loaded modules.
-  $requirements = module_invoke_all('requirements', 'update');
-  $requirements += update_extra_requirements();
-  $severity = drupal_requirements_severity($requirements);
-
-  // If there are errors, always display them. If there are only warnings, skip
-  // them if the caller has indicated they should be skipped.
-  if ($severity == REQUIREMENT_ERROR || ($severity == REQUIREMENT_WARNING && !$skip_warnings)) {
-    update_task_list('requirements');
-    drupal_set_title('Requirements problem');
-    $status_report = theme('status_report', array('requirements' => $requirements));
-    $status_report .= 'Check the messages and <a href="' . check_url(drupal_requirements_url($severity)) . '">try again</a>.';
-    print theme('update_page', array('content' => $status_report));
-    exit();
-  }
-}
-
-// Some unavoidable errors happen because the database is not yet up-to-date.
-// Our custom error handler is not yet installed, so we just suppress them.
-ini_set('display_errors', FALSE);
-
-// We prepare a minimal bootstrap for the update requirements check to avoid
-// reaching the PHP memory limit.
-require_once DRUPAL_ROOT . '/core/includes/bootstrap.inc';
-require_once DRUPAL_ROOT . '/core/includes/update.inc';
-require_once DRUPAL_ROOT . '/core/includes/common.inc';
-require_once DRUPAL_ROOT . '/core/includes/file.inc';
-require_once DRUPAL_ROOT . '/core/includes/unicode.inc';
-require_once DRUPAL_ROOT . '/core/includes/schema.inc';
-update_prepare_d8_bootstrap();
-
-// Determine if the current user has access to run update.php.
-drupal_bootstrap(DRUPAL_BOOTSTRAP_SESSION);
-
-// A request object from the HTTPFoundation to tell us about the request.
-// @todo These two lines were copied from index.php which has its own todo about
-// a change required here. Revisit this when that change has been made.
-$request = Request::createFromGlobals();
-
-// There can be conflicting 'op' parameters because both update and batch use
-// this parameter name. We need the 'op' coming from a POST request to trump
-// that coming from a GET request.
-$op = $request->request->get('op');
-if (is_null($op)) {
-  $op = $request->query->get('op');
-}
-
-// Only allow the requirements check to proceed if the current user has access
-// to run updates (since it may expose sensitive information about the site's
-// configuration).
-if (is_null($op) && update_access_allowed()) {
-  require_once DRUPAL_ROOT . '/core/includes/install.inc';
-  require_once DRUPAL_ROOT . '/core/modules/system/system.install';
-
-  // Load module basics.
-  include_once DRUPAL_ROOT . '/core/includes/module.inc';
-  $module_list['system']['filename'] = 'core/modules/system/system.module';
-  module_list(NULL, $module_list);
-  drupal_load('module', 'system');
-
-  // Reset the module_implements() cache so that any new hook implementations
-  // in updated code are picked up.
-  module_implements_reset();
-
-  // Set up $language, since the installer components require it.
-  drupal_language_initialize();
-
-  // Set up theme system for the maintenance page.
-  drupal_maintenance_theme();
-
-  // Check the update requirements for Drupal. Only report on errors at this
-  // stage, since the real requirements check happens further down.
-  update_check_requirements(TRUE);
-
-  // Redirect to the update information page if all requirements were met.
-  install_goto('core/update.php?op=info');
-}
-
-// Allow update_fix_d8_requirements() to run before code that can break on a
-// Drupal 7 database.
-drupal_bootstrap(DRUPAL_BOOTSTRAP_CODE);
-update_fix_d8_requirements();
-drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);
-drupal_maintenance_theme();
-
-// Turn error reporting back on. From now on, only fatal errors (which are
-// not passed through the error handler) will cause a message to be printed.
-ini_set('display_errors', TRUE);
-
-
-// Only proceed with updates if the user is allowed to run them.
-if (update_access_allowed()) {
-
-  include_once DRUPAL_ROOT . '/core/includes/install.inc';
-  include_once DRUPAL_ROOT . '/core/includes/batch.inc';
-  drupal_load_updates();
-
-  update_fix_compatibility();
-
-  // Check the update requirements for all modules. If there are warnings, but
-  // no errors, skip reporting them if the user has provided a URL parameter
-  // acknowledging the warnings and indicating a desire to continue anyway. See
-  // drupal_requirements_url().
-  $continue = $request->query->get('continue');
-  $skip_warnings = !empty($continue);
-  update_check_requirements($skip_warnings);
-
-  switch ($op) {
-    // update.php ops.
-
-    case 'selection':
-      $token = $request->query->get('token');
-      if (isset($token) && drupal_valid_token($token, 'update')) {
-        $output = update_selection_page();
-        break;
-      }
-
-    case 'Apply pending updates':
-      $token = $request->query->get('token');
-      if (isset($token) && drupal_valid_token($token, 'update')) {
-        // Generate absolute URLs for the batch processing (using $base_root),
-        // since the batch API will pass them to url() which does not handle
-        // update.php correctly by default.
-        $batch_url = $base_root . drupal_current_script_url();
-        $redirect_url = $base_root . drupal_current_script_url(array('op' => 'results'));
-        update_batch($request->request->get('start'), $redirect_url, $batch_url);
-        break;
-      }
-
-    case 'info':
-      $output = update_info_page();
-      break;
-
-    case 'results':
-      $output = update_results_page();
-      break;
-
-    // Regular batch ops : defer to batch processing API.
-    default:
-      update_task_list('run');
-      $output = _batch_page();
-      break;
-  }
-}
-else {
-  $output = update_access_denied_page();
-}
-if (isset($output) && $output) {
-  // Explicitly start a session so that the update.php token will be accepted.
-  drupal_session_start();
-  // We defer the display of messages until all updates are done.
-  $progress_page = ($batch = batch_get()) && isset($batch['running']);
-  if ($output instanceof Response) {
-    $output->send();
-  }
-  else {
-    print theme('update_page', array('content' => $output, 'show_messages' => !$progress_page));
-  }
-}
+update_drupal();
