oktags (rubygems): oktags helps you organize your files by managing tags on them. It works by adding/removing at the end of the filename. Given a file 'cat.jpg', when adding the tags 'tag1' and 'tag2', the filename will become 'cat--[tag1,tag2].jpg'. The implementation is OS-agnostic, so it should work on Linux, macOS and Windows. 
Keywords: commandline|filesystem|ruby|tagging