Index: wp-includes/plugin.php
===================================================================
--- wp-includes/plugin.php	(revision 15667)
+++ wp-includes/plugin.php	(working copy)
@@ -668,6 +668,46 @@
 }
 
 /**
+ * Register a routine to be called when a plugin has been updated
+ *
+ * It works by comparing the current version with the version previously stored in the database.
+ *
+ * @since 3.1
+ *
+ * @param string $file A reference to the main plugin file
+ * @param callback $callback The function to run when the hook is called.
+ * @param string $version The version to which the plugin is updating.
+ */
+function register_update_hook( $file, $callback, $version ) {
+	if ( !is_admin() )
+		return;
+
+	$plugin = plugin_basename( $file );
+
+	if ( is_plugin_active_for_network( $plugin ) ) {
+		$current_vers = get_site_option( 'active_plugin_versions', array() );
+		$network = true;
+	} elseif ( is_plugin_active( $plugin ) ) {
+		$current_vers = get_option( 'active_plugin_versions', array() );
+		$network = false;
+	} else {
+		return false;
+	}
+
+	if ( version_compare( $version, $current_vers[ $plugin ], '>' ) ) {
+		call_user_func( $callback, $current_vers[ $plugin ], $network );
+
+		$current_vers[ $plugin ] = $version;
+	}
+
+	if ( $network ) {
+		update_site_option( 'active_plugin_versions', $current_vers );
+	} else {
+		update_option( 'active_plugin_versions', $current_vers );
+	}
+}
+
+/**
  * Calls the 'all' hook, which will process the functions hooked into it.
  *
  * The 'all' hook passes all of the arguments or parameters that were used for