My databases are each many collections, but some do not need backing up (they are thumbnails and similar)

I'd like an option to mongodump to specifically exclude some collections, ideally some sort of prefix or glob wildcard. Some of these collections are actually gridfs hence more convoluted names. Something like this would be great:

mongodump --exclude-collections 'thumbnails*'

It is also far easier to do this (blacklisting) than listing what I do want (whitelisting, current command line flags) since the collection names change all the time and it would be a pain to track.