Mark a file as “do not backup”

I’m a plugin author. My plugin writes a temporary file (by default in WP_CONTENT), which doesn’t need to be backed up and shouldn’t be restored from backup.

Do you have a filter or any such mechanism my plugin can hook so I can tell your plugin to avoid backing it up?

I believe you skip a directory if it contains a .donotbackup file. But I’d rather not guess about this. Any suggestions?