materio-base-d7/sites/all/modules/contrib/admin/workflow/workflow_revert/workflow_revert.module

<?php
/**
 * @file
 * Adds an 'Revert' link to the first workflow history row.
 */

/**
 * Implements hook_permission().
 */
function workflow_revert_permission() {
  return array(
    'revert workflow' => array(
      'title' => t('Revert workflow'),
      'description' => t('Allow user to revert workflow state.'),
      ),
    );
}

/**
 * Implements hook_menu().
 */
function workflow_revert_menu() {
  $items = array();

  $items['workflow_revert'] = array(
    'title' => 'Workflow Undo',
    'access arguments' => array('revert workflow'),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('workflow_revert_form'),
    'type' => MENU_CALLBACK,
    );

  return $items;
}

/**
 * Menu callback to do the revert function.
 */
function workflow_revert_form($form, $form_state, $nid = NULL, $sid = NULL) {
  $args = array('#nid' => $nid, '#sid' => $sid);

  if (drupal_valid_token($_GET['token'], 'workflow_revert ' . $sid)) {
    $states = workflow_get_workflow_states_all();
    $node = node_load($nid);
    $args['#node'] = $node;
    $question = t('Are you sure you want to revert %title to the "@state" state?', array(
      '@state' => $states[$sid],
      '%title' => $node->title,
      ));
    return confirm_form($args,
      $question,
      "node/$nid",
      t('The worflow state will be changed.')
      );
  }
  else {
    watchdog('workflow_revert', 'Invalid token', array(), WATCHDOG_ERROR);
    drupal_set_message(t('Invalid token. Your information has been recorded.'), 'error');
    drupal_goto("node/$nid");
  }
}

function workflow_revert_form_submit($form, $form_state) {
  $node = $form['#node'];
  $comment = t('State reverted');
  $sid = $form['#sid'];

  // Force the transition because it's probably not valid.
  workflow_execute_transition($node, $sid, $comment, TRUE);
  drupal_set_message(t('Workflow reverted.', array()));

  drupal_goto('node/' . $form['#nid'] . '/workflow');
}

/**
 * Implements hook_workflow_history_alter().
 * Add an 'undo' operation for the most recent history change.
 *
 * @param $variables
 *   The current workflow history information as an array.
 *   'old_sid' - The state ID of the previous state.
 *   'old_state_name' - The state name of the previous state.
 *   'sid' - The state ID of the current state.
 *   'state_name' - The state name of the current state.
 *   'history' - The row from the workflow_node_history table.
 *
 * If you want to add additional data, place it in the 'extra' value.
 */
function workflow_revert_workflow_history_alter(&$variables) {
  static $first = TRUE;
  // Only mark the first row.
  if ($first) {
    // Let's ask other modules if the reversion is allowed.
    $node = node_load($variables['history']->nid);
    $result = module_invoke_all('workflow', 'transition permitted', $variables['sid'], $variables['old_sid'], $node);
    // Did anybody veto this choice?
    if (!in_array(FALSE, $result)) {
      // If not vetoed, mark it.
      $options = array('query' => array('token' => drupal_get_token('workflow_revert ' . $variables['old_sid'])));
      $path = 'workflow_revert/' . $variables['history']->nid . '/' . $variables['old_sid'];
      $variables['extra'] = l('Revert state change', $path, $options);
    }
    // That was your one chance...
    $first = FALSE;
  }
}