Introduce email templates for automatic background updates.

The four templates are:
 1. We successfully updated their site. If any of their themes or plugins are out of date, it also mentions that. ('success')
 2. We are not configured to update their site, so we notify them of the new release. ('notify')
 3. We tried but failed to update their site. The error was early in the process, so no harm, no foul. This is the same as template #2, plus one sentence. ('fail')
 4. We tried to update their site, and failed while copying files. ('critical')

With assistance from markjaquith.

see #10787.

Built from https://develop.svn.wordpress.org/trunk@25837


git-svn-id: http://core.svn.wordpress.org/trunk@25749 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-upgrader.php

@@ -1836,8 +1836,103 @@ class WP_Automatic_Updater {
 		delete_option( $lock_name );
 	}
 
-	function send_debug_email() {
+	protected function send_email( $type, $core_update, $result = null ) {
+		if ( ! apply_filters( 'automatic_updates_send_email', true, $type, $core_update, $result ) )
+			return;
 
+		switch ( $type ) {
+			case 'success' : // We updated.
+				/* translators: 1: Site name, 2: WordPress version number. */
+				$subject = __( '[%1$s] Your site has updated to WordPress %2$s' );
+				break;
+
+			case 'fail' :   // We tried to update but couldn't.
+			case 'manual' : // We can't update (and made no attempt).
+				/* translators: 1: Site name, 2: WordPress version number. */
+				$subject = __( '[%1$s] WordPress %2$s is available. Please update!' );
+				break;
+
+			case 'critical' : // We tried to update, started to copy files, then things went wrong.
+				/* translators: 1: Site name. */
+				$subject = __( '[%1$s] URGENT: Your site may be down due to a failed update' );
+				break;
+
+			default :
+				return;
+		}
+
+		$subject = sprintf( $subject, wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ), $core_update->current );
+
+		$body = '';
+
+		switch ( $type ) {
+			case 'success' :
+				$body .= sprintf( __( 'Howdy! Your site at %1$s has been updated automatically to WordPress %2$s.' ), home_url(), $core_update->current );
+				$body .= "\n\n" . __( 'No further action is needed on your part.' );
+
+				// Can only reference the About screen if their update was successful.
+				list( $about_version ) = explode( '-', $core_update->current, 2 );
+				$body .= ' ' . sprintf( __( "For more on version %s, see the About WordPress screen:" ), $about_version );
+				$body .= "\n" . admin_url( 'about.php' );
+				break;
+
+			case 'fail' :
+			case 'manual' :
+				$body .= sprintf( __( 'Please update your site at %1$s to WordPress %2$s.' ), home_url(), $core_update->current );
+
+				$body .= "\n\n";
+				if ( 'fail' == $type )
+					$body .= __( 'We tried but were unable to update your site automatically.' ) . ' ';
+				$body .= __( 'Updating is easy and only takes a few moments:' );
+				$body .= "\n" . network_admin_url( 'update-core.php' );
+				break;
+
+			case 'critical' :
+				$body .= sprintf( __( 'Your site at %1$s experienced a critical failure while trying to update to the latest version of WordPress, %2$s.' ), home_url(), $core_update->current );
+
+				$body .= "\n\n" . __( "This means your site may be offline or broken. Don't panic; this can be fixed." );
+
+				$body .= "\n\n" . __( "Please check out your site now. It's possible that everything is working. If it says you need to update, you should do so:" );
+				$body .= "\n" . network_admin_url( 'update-core.php' );
+				break;
+		}
+
+		// Updates are important!
+		if ( $type != 'success' )
+			$body .= "\n\n" . __( 'Keeping your site updated is important for security. It also makes the internet a safer place for you and your readers.' );
+
+		// Add a note about the support forums to all emails.
+		$body .= "\n\n" . __( 'If you experience any issues or need support, the volunteers in the WordPress.org support forums may be able to help.' );
+		$body .= "\n" . __( 'http://wordpress.org/support/' );
+
+		// If things are successful, mention plugins and themes if any are out of date.
+		if ( $type == 'success' && ( get_plugin_updates() || get_theme_updates() ) ) {
+			$body .= "\n\n" . __( 'You also have some plugins or themes with updates available. Update them now:' );
+			$body .= "\n" . network_admin_url();
+		}
+
+		$body .= "\n\n" . __( 'The WordPress Team' ) . "\n";
+
+		if ( 'critical' == $type && is_wp_error( $result ) ) {
+			$body .= "\n***\n\n";
+			$body .= __( 'We have some data that describes the error your site encountered.' );
+			$body .= ' ' . __( 'Your hosting company, support forum volunteers, or a friendly developer may be able to use this information to help you:' );
+			$body .= "\n" . sprintf( __( "Error code: %s" ), $result->get_error_code() );
+			$body .= "\n" . $result->get_error_message();
+			$body .= "\n" . implode( ', ', (array) $result->get_error_data() );
+			$body .= "\n";
+		}
+
+		$to  = get_site_option( 'admin_email' );
+		$headers = '';
+
+		$email = compact( 'to', 'body', 'subject', 'headers' );
+		$email = apply_filters( 'automatic_update_send_email', $email, $type, $core_update, $result );
+
+		wp_mail( $email['to'], $email['subject'], $email['body'], $email['headers'] );
+	}
+
+	protected function send_debug_email() {
 		if ( empty( $this->update_results ) )
 			return;
 
@@ -1913,8 +2008,11 @@ class WP_Automatic_Updater {
 				$body[] = str_repeat( '-', strlen( $update->name ) );
 				foreach ( $update->messages as $message )
 					$body[] = "  " . html_entity_decode( str_replace( '…', '...', $message ) );
-				if ( is_wp_error( $update->result ) )
+				if ( is_wp_error( $update->result ) ) {
 					$body[] = '  Error: [' . $update->result->get_error_code() . '] ' . $update->result->get_error_message();
+					if ( $update->result->get_error_data() )
+						$body[] = '         ' . implode( ', ', (array) $update->result->get_error_data() );
+				}
 				$body[] = '';
 			}
 		}