Don't warn about a .maintenance file in the root directory (#114)

* don't warn about .maintenance file

* fix: add tests for .maintenance

Author: paulschreiber

features/checksum-core.feature

@@ -151,6 +151,11 @@ Feature: Validate checksums for WordPress install
       """
       # BEGIN WordPress
       """
+    And a .maintenance file:
+      """
+      <?php
+      $upgrading = time();
+      """
     And a extra-file.php file:
       """
       hello world
@@ -177,6 +182,10 @@ Feature: Validate checksums for WordPress install
       """
       Warning: File should not exist: .htaccess
       """
+    And STDERR should not contain:
+      """
+      Warning: File should not exist: .maintenance
+      """
     And STDERR should not contain:
       """
       Warning: File should not exist: wp-content/unknown-file.php

src/Checksum_Core_Command.php

@@ -151,7 +151,7 @@ public function __invoke( $args, $assoc_args ) {
 	 */
 	protected function filter_file( $filepath ) {
 		if ( true === $this->include_root ) {
-			return ( 1 !== preg_match( '/^(\.htaccess$|wp-config\.php$|wp-content\/)/', $filepath ) );
+			return ( 1 !== preg_match( '/^(\.htaccess$|\.maintenance$|wp-config\.php$|wp-content\/)/', $filepath ) );
 		}
 
 		return ( 0 === strpos( $filepath, 'wp-admin/' )