updated comment

Author: baa-ableton

src/uu/cp/src/copydir.rs

@@ -669,7 +669,7 @@ fn build_dir(
         excluded_perms |= umask;
         // Always keep the owner write bit so we can copy files into the directory.
         // The correct final permissions are applied afterward by dirs_needing_permissions.
-        let mode = (!excluded_perms & 0o777) | 0o200; //use only the last three octet bits
+        let mode = (!excluded_perms & 0o777) | 0o200; // mask to permission bits, always keep owner write
         std::os::unix::fs::DirBuilderExt::mode(&mut builder, mode);
     }