What does drupal_clone($node) do in Drupal? Will it clone a node? I know the node will be saved only if node_save($clone) is rendered. So what will happen when drupal_clone($node) is rendered ?

/**
 * Generate a node preview.
 */
function node_preview($node) {
    if (node_access('create', $node) || node_access('update', $node)) {
        // Load the user's name when needed.
        if (isset($node->name)) {
            // The use of isset() is mandatory in the context of user IDs, because
            // user ID 0 denotes the anonymous user.
            if ($user = user_load(array('name' => $node->name))) {
                $node->uid = $user->uid;
                $node->picture = $user->picture;
            } else {
                $node->uid = 0; // anonymous user
            }
        } else if ($node->uid) {
            $user = user_load(array('uid' => $node->uid));
            $node->name = $user->name;
            $node->picture = $user->picture;
        }

        $node->changed = time();

        // Extract a teaser, if it hasn't been set (e.g. by a module-provided
        // 'teaser' form item).
        if (!isset($node->teaser)) {
            $node->teaser = empty($node->body) ? '' : node_teaser($node->body, $node->format);
            // Chop off the teaser from the body if needed.
            if (!$node->teaser_include && $node->teaser == substr($node->body, 0, strlen($node->teaser))) {
                $node->body = substr($node->body, strlen($node->teaser));
            }
        }

        // Display a preview of the node.
        // Previewing alters $node so it needs to be cloned.
        if (!form_get_errors()) {
            $cloned_node = drupal_clone($node);
            $cloned_node->build_mode = NODE_BUILD_PREVIEW;
            $output = theme('node_preview', $cloned_node);
        }
        drupal_set_title(t('Preview'));

        return $output;
    }
}

Real Issue

I am getting the node cloned when clicking the preview button. Is it related to any code changes?