From 32d38fc0807b5110367ca8b593951af3213818c9 Mon Sep 17 00:00:00 2001
From: John Blackbourn <johnbillion@git.wordpress.org>
Date: Wed, 29 Oct 2014 19:01:15 +0000
Subject: [PATCH] Introduce some actions and filters which aid plugins in
 revisioning post meta.

 * `wp_save_post_revision_post_has_changed` filter which can be used to determine if a post has been changed, and therefore if a revision should be created for a post.
 * `wp_get_revision_ui_diff` filter which can be used to filter the fields displayed in the post revision diff UI.
 * `wp_creating_autosave` action which is fired just before an autosave is created.

See #20564.
Props mattheu, adamsilverstein.


git-svn-id: https://develop.svn.wordpress.org/trunk@30091 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-admin/includes/post.php     |  9 +++++++++
 src/wp-admin/includes/revision.php | 13 ++++++++++++-
 src/wp-includes/revision.php       | 19 ++++++++++++++++++-
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/src/wp-admin/includes/post.php b/src/wp-admin/includes/post.php
index 4cfad6ed87..486282ac2a 100644
--- a/src/wp-admin/includes/post.php
+++ b/src/wp-admin/includes/post.php
@@ -1541,6 +1541,15 @@ function wp_create_post_autosave( $post_data ) {
 			return 0;
 		}
 
+		/**
+		 * Fires before an autosave is stored.
+		 *
+		 * @since 4.1.0
+		 *
+		 * @param array $new_autosave Post array - the autosave that is about to be saved.
+		 */
+		do_action( 'wp_creating_autosave', $new_autosave );
+
 		return wp_update_post( $new_autosave );
 	}
 
diff --git a/src/wp-admin/includes/revision.php b/src/wp-admin/includes/revision.php
index 151cd64454..4e20f2d608 100644
--- a/src/wp-admin/includes/revision.php
+++ b/src/wp-admin/includes/revision.php
@@ -92,7 +92,18 @@ function wp_get_revision_ui_diff( $post, $compare_from, $compare_to ) {
 			);
 		}
 	}
-	return $return;
+
+	/**
+	 * Filter the fields displayed in the post revision diff UI.
+	 *
+	 * @since 4.1.0
+	 *
+	 * @param array   $return       Revision UI fields. Each item is an array of id, name and diff.
+	 * @param WP_Post $compare_from The revision post to compare from.
+	 * @param WP_Post $compare_to   The revision post to compare to.
+	 */
+	return apply_filters( 'wp_get_revision_ui_diff', $return, $compare_from, $compare_to );
+
 }
 
 /**
diff --git a/src/wp-includes/revision.php b/src/wp-includes/revision.php
index 45e436f567..68ad112683 100644
--- a/src/wp-includes/revision.php
+++ b/src/wp-includes/revision.php
@@ -133,9 +133,26 @@ function wp_save_post_revision( $post_id ) {
 					break;
 				}
 			}
+
+			/**
+			 * Filter whether a post has changed.
+			 *
+			 * By default a revision is saved only if one of the revisioned fields has changed.
+			 * This filter allows for additional checks to determine if there were changes.
+			 *
+			 * @since 4.1.0
+			 *
+			 * @param bool    $post_has_changed Whether the post has changed.
+			 * @param WP_Post $last_revision    The the last revision post object.
+			 * @param WP_Post $post             The post object.
+			 *
+			 */
+			$post_has_changed = (bool) apply_filters( 'wp_save_post_revision_post_has_changed', $post_has_changed, $last_revision, $post );
+
 			//don't save revision if post unchanged
-			if( ! $post_has_changed )
+			if( ! $post_has_changed ) {
 				return;
+			}
 		}
 	}