Purge only happens if filesize is different

Problem/Motivation

The module only purges when the file size is different. Per this line of code in purge_file.module, in the function purge_file_file_update().

    && ($file->getFileUri() != $original_file->getFileUri() || $file->getSize() != $original_file->getSize())) {

This is fine for 99.9% of use casese. However, a valid use case when updating a file may be to go in, and only change a few characters, that net the same filesize. Such as

Reviewed on: 01/30/2026

I might suggest we use something like the php function hash_file() here. If performance is a concern, maybe this can be run only when we determine that the filesize between the new and old versions are the same. I'm not sure if hash_file is efficient though, and I am concerned this could cause memory limit issues for larger files, so maybe there are better ways about it, like checking the mtime.

Alternatively, maybe we can make it a configuration option to just always send purges for any file update, and let the user decide if they need it or not.