WordPress at a glance
filter is not described

wp_save_post_revision_check_for_changes filter-hook . WP 3.6.0

Filters whether the post has changed since the last revision.

By default a revision is saved only if one of the revisioned fields has changed. This filter can override that so a revision is saved even if nothing has changed.

Usage

add_filter( 'wp_save_post_revision_check_for_changes', 'filter_function_name_409', 10, 3 );
function filter_function_name_409( $check_for_changes, $last_revision, $post ){
	// filter...

	return $check_for_changes;
}
$check_for_changes(true/false)
Whether to check for changes before saving a new revision.
Default: true
$last_revision(WP_Post)
The last revision post object.
$post(WP_Post)
The post object.

Where the hook is called

wp_save_post_revision()
wp-includes/revision.php 154
if ( isset( $last_revision ) && apply_filters( 'wp_save_post_revision_check_for_changes', $check_for_changes = true, $last_revision, $post ) ) {

Where the hook is used (in WP core)

Does not used.