g.command 'upload' do |c|
          c.flag 'channels', desc: 'Comma-separated list of channel names or IDs where the file will be shared.'
          c.flag 'content', desc: 'File contents via a POST variable. If omitting this parameter, you must provide a file.'
          c.flag 'file', desc: 'File contents via multipart/form-data. If omitting this parameter, you must submit content.'
          c.flag 'filename', desc: 'Filename of file.'