Description:
Creates a new node revision upon flagging a node with the Flag module and displays flag type (name + flag/unflagged) in revision log. Benefit: Rules module installation no longer required for that specific purpose.

Requires:

• Drupal 6.x
• Revisions enabled
• Flag module 6.x-1.x

Usage
Create a new .module file -- like flag_revision.module and the respective flag_revision.info file.

Code
Put this in your just created flag_revision.module file.

<?php

function flag_revision_action_info()
{
	$info['flag_revision_create_revision_action'] = array(
		'type' 			=> 'node',
		'description'	=> t('Create new revision'),
		'configurable'	=> FALSE,
		'behavior' => array('changes_node_property'),
		'hooks' => array(
			'flag' => TRUE,
		),
	);

	return $info;
}

function flag_revision_create_revision_action($object, $context)
{
	$object->revision = 1;
	$flag = flag_get_flag($context['flag-action']->flag);
	$object->log = t((($context['flag-action']->action == 'flag')?'Flagged - @flag_title':'Unflagged - @flag_title'),array('@flag_title' => $flag->get_title()));
}

The end
Save, upload to modules folder and active it. The "Create new revision" action can now be associated with a flag from -> Flags ->Actions.