A standard Drupal install does not allow you to create a "Pending" revision. You have two options:
- Programatically create a new revision but programatically revert back to the original revision (which creates an even newer revision, but it has the original content)
- (Recommended) Use Workbench Moderation, Revisioning or Workflow which are well thought-out solutions for version control and/or access control.
For option 1:
You can add this code as a new Rule or use it in a new module
<?php
// Programatically load the existing revision and save it
// Taken from http://api.drupal.org/api/drupal/modules!node!node.module/function/node_save/7
// Load the revision
$original_revision = node_load($nid);
$original_revision->revision = 1;
$original_revision->log = t('Copy of the revision from %date.', array('%date' => format_date($original_revision->revision_timestamp)));
$new_revision = node_load($nid);
// Make any changes to the new revision here...
$new_revision->revision = 1;
$new_revision->log = t('Summarize your changes here');
// Save the new revision first
node_save($new_revision);
// Save the original one again so that it is still the current revision
node_save($original_revision);
watchdog('content', '@type: reverted %title revision %revision.', array('@type' => $node_revision->type, '%title' => $node_revision->title, '%revision' => $node_revision->vid));
drupal_set_message(t('@type %title was saved with a new revision, but reverting to original revision from %revision-date.', array('@type' => node_type_get_name($node_revision), '%title' => $node_revision->title, '%revision-date' => format_date($node_revision->revision_timestamp))));
drupal_goto('node/' . $node_revision->nid . '/revisions');
?>
For option 2:
I would recommend Workbench over Revisioning or Workflow, but each is different depending on your needs. Workbench is kind of the successor to Revisioning, and Workflow is a lot more than just version control, so it may or may not be a good fit for your needs.
Here's a quick breakdown on the differences between Workbench and Workflow.