There's an open-source multi-platform client, written in Go: drive. It's quite nice and full-featured, and also is in active development.
$ drive help pull
Name
pull - pulls remote changes from Google Drive
Description
Downloads content from the remote drive or modifies
local content to match that on your Google Drive
Note: You can skip checksum verification by passing in flag `-ignore-checksum`
* For usage flags: `drive pull -h`