Index: src/wp-includes/revision.php
===================================================================
--- src/wp-includes/revision.php	(revision 27694)
+++ src/wp-includes/revision.php	(working copy)
@@ -16,8 +16,6 @@
  * @since 2.6.0
  * @access private
  *
- * @uses apply_filters() Calls '_wp_post_revision_fields' on 'title', 'content' and 'excerpt' fields.
- *
  * @param array $post Optional a post array to be processed for insertion as a post revision.
  * @param bool $autosave optional Is the revision an autosave?
  * @return array Post array ready to be inserted as a post revision or array of fields that can be versioned.
@@ -33,7 +31,21 @@
 			'post_excerpt' => __( 'Excerpt' ),
 		);
 
-		// Runs only once
+		/**
+		 * Filter the list of fields saved in post revisions.
+		 *
+		 * Included by default: 'post_title', 'post_content' and 'post_excerpt'.
+		 *
+		 * Disallowed fields: 'ID', 'post_name', 'post_parent', 'post_date',
+		 * 'post_date_gmt', 'post_status', 'post_type', 'comment_count',
+		 * and 'post_author'.
+		 *
+		 * @since 2.6.0
+		 *
+		 * @param array $fields List of fields to revision. Contains 'post_title',
+		 *                      'post_content', and 'post_excerpt' by default.
+		 *
+		 */
 		$fields = apply_filters( '_wp_post_revision_fields', $fields );
 
 		// WP uses these internally either in versioning or elsewhere - they cannot be versioned
@@ -99,7 +111,21 @@
 			}
 		}
 
-		if ( isset( $last_revision ) && apply_filters( 'wp_save_post_revision_check_for_changes', true, $last_revision, $post ) ) {
+		/**
+		 * Filter 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.
+		 *
+		 * @since 3.6.0
+		 *
+		 * @param bool $check_for_changes Whether to check for changes before saving a new revision.
+		 *                                Default true.
+		 * @param int  $last_revision     ID of the last revision.
+		 * @param int  $post              Post ID.
+		 *
+		 */
+		if ( isset( $last_revision ) && apply_filters( 'wp_save_post_revision_check_for_changes', $check_for_changes = true, $last_revision, $post ) ) {
 			$post_has_changed = false;
 
 			foreach ( array_keys( _wp_post_revision_fields() ) as $field ) {
@@ -237,8 +263,16 @@
 	if ( is_wp_error($revision_id) )
 		return $revision_id;
 
-	if ( $revision_id )
+	if ( $revision_id ) {
+		/**
+		 * Fires once a revision has been saved.
+		 *
+		 * @since 2.6.0
+		 *
+		 * @param int $revision_id Post revision ID.
+		 */
 		do_action( '_wp_put_post_revision', $revision_id );
+	}
 
 	return $revision_id;
 }
@@ -283,8 +317,6 @@
  *
  * @uses wp_get_post_revision()
  * @uses wp_update_post()
- * @uses do_action() Calls 'wp_restore_post_revision' on post ID and revision ID if wp_update_post()
- *  is successful.
  *
  * @param int|object $revision_id Revision ID or revision object.
  * @param array $fields Optional. What fields to restore from. Defaults to all.
@@ -324,6 +356,14 @@
 	// Update last edit user
 	update_post_meta( $post_id, '_edit_last', get_current_user_id() );
 
+	/**
+	 * Fires after a post revision has been restored.
+	 *
+	 * @since 2.6.0
+	 *
+	 * @param int $post_id     Post ID.
+	 * @param int $revision_id Post revision ID.
+	 */
 	do_action( 'wp_restore_post_revision', $post_id, $revision['ID'] );
 
 	return $post_id;
@@ -350,8 +390,17 @@
 	if ( is_wp_error( $delete ) )
 		return $delete;
 
-	if ( $delete )
+	if ( $delete ) {
+		/**
+		 * Fires once a post revision has been deleted.
+		 *
+		 * @since 2.6.0
+		 *
+		 * @param int          $revision_id Post revision ID.
+		 * @param object|array $revision    Post revision object or array.
+		 */
 		do_action( 'wp_delete_post_revision', $revision->ID, $revision );
+	}
 
 	return $delete;
 }
@@ -406,7 +455,6 @@
  * @since 3.6.0
  *
  * @uses post_type_supports()
- * @uses apply_filters() Calls 'wp_revisions_to_keep' hook on the number of revisions.
  *
  * @param object $post The post object.
  * @return int The number of revisions to keep.
@@ -422,6 +470,16 @@
 	if ( ! post_type_supports( $post->post_type, 'revisions' ) )
 		$num = 0;
 
+	/**
+	 * Filter the number of revisions to save for the given post.
+	 *
+	 * Overrides the value of WP_POST_REVISIONS.
+	 *
+	 * @since 3.6.0
+	 *
+	 * @param int     $num  Number of revisions to store.
+	 * @param WP_Post $post Post object.
+	 */
 	return (int) apply_filters( 'wp_revisions_to_keep', $num, $post );
 }