I’m sorry to say that I would pay for the feature. I’m sorry about it because I shouldn’t have to, but no sync app seems interested in doing anything about it except for Insync’s very welcome, but sadly limited extension-based ignore list.
If not a pattern list, at the very least, arbitrary folder names (‘temp’, ‘tmp’, ‘log’, etc.) in addition to extensions should be an integral feature. It’s absolutely necessary in order to sync code development workstations efficiently for the same reason that git has a pattern-based ignore list. Without it, syncing is a huge PITA that I’ve been trying to work around since Ubuntu One went under. Their Linux version did exactly what @peci1 and I want - it accommodated a list of regex patterns to ignore.
Bottom line is I guess there isn’t a business case for this simple feature because it’s not really necessary for the predominant file-sharing paradigm. It’s important enough to the tiny market that is “me” that I’m about to abandon Insync for my dev work (the best of the bunch, but not good enough for my needs) and attempt to write my own lame Drive app. I’m tired of dealing with this limitation for a year now trying to keep my workstations in sync, seeing my CPU capacity and internet connection sucked up to process umpteen cache files (does “sprockets” ring a bell?), log files, map tiles, dump files, etc. etc to upload at the pathetic speeds ISP’s offer.