Exclude from exclude list
I've got a case where some brilliant plugin developers have elected to store code in a folder called "logs". We have the recommended backup exclusions in place, including logs/* which means this code is not being backed up. since there's basically no way to predict when a random plugin developer is going to do this, using the current exclusions system means we either have to backup all log files, or scan user directories for log files and add them explicitly. This is impractical on a server with a large number of accounts.
This is complicated by some CMS systems and frameworks that write their log files with a .php extension to prevent attackers from reading the contents.
I propose one of two solutions: either allow a "negative exclude" along the lines of:
Or add a hook that gets called before every file that returns a bool false if the file should be skipped.