Show the nag we show for a stuck .maintenance file when an auto update failed.

see #25654.

Built from https://develop.svn.wordpress.org/trunk@25872


git-svn-id: http://core.svn.wordpress.org/trunk@25872 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/update.php

@@ -344,8 +344,27 @@ function wp_theme_update_row( $theme_key, $theme ) {
 }
 
 function maintenance_nag() {
+	include ABSPATH . WPINC . '/version.php'; // include an unmodified $wp_version
 	global $upgrading;
-	if ( ! isset( $upgrading ) )
+	$nag = isset( $upgrading );
+	if ( ! $nag ) {
+		$failed = get_site_option( 'auto_core_update_failed' );
+		/*
+		 * If an update failed critically, we may have copied over version.php but not other files.
+		 * In that case, if the install claims we're running the version we attempted, nag.
+		 * This is serious enough to err on the side of nagging.
+		 *
+		 * If we simply failed to update before we tried to copy any files, then assume things are
+		 * OK if they are now running the latest.
+		 *
+		 * This flag is cleared whenever a successful update occurs using Core_Upgrader.
+		 */
+		$comparison = ! empty( $failed['critical'] ) ? '>=' : '>';
+		if ( version_compare( $failed['attempted'], $wp_version, '>=' ) )
+			$nag = true;
+	}
+
+	if ( ! $nag )
 		return false;
 
 	if ( current_user_can('update_core') )
@@ -356,3 +375,4 @@ function maintenance_nag() {
 	echo "<div class='update-nag'>$msg</div>";
 }
 add_action( 'admin_notices', 'maintenance_nag' );
+add_action( 'network_admin_notices', 'maintenance_nag' );