Filesystem API: Avoid chmod() warnings if the permissions already match.

This prevents spurious warnings from `WP_Filesystem_Direct::chmod()` when the web process doesn't have ownership over the files, and thus cannot change the permissions, even if only to reassert the existing mode.

Follow-up to [6779], [11667], [12998].

Props redsweater, mukesh27, SergeyBiryukov.
Fixes #64610.

git-svn-id: https://develop.svn.wordpress.org/trunk@61601 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-admin/includes/class-wp-filesystem-direct.php

@@ -170,6 +170,22 @@ public function chmod( $file, $mode = false, $recursive = false ) {
 		}
 
 		if ( ! $recursive || ! $this->is_dir( $file ) ) {
+			$current_mode = fileperms( $file ) & 0777 | 0644;
+
+			/*
+			 * fileperms() populates the stat cache, so have to clear it
+			 * to maintain parity with the previous behavior.
+			 */
+			clearstatcache( true, $file );
+
+			/*
+			 * Avoid calling chmod() if the requested mode is already set,
+			 * to prevent throwing a warning when we aren't the owner.
+			 */
+			if ( $current_mode === $mode ) {
+				return true;
+			}
+
 			return chmod( $file, $mode );
 		}