I thought about this, but I accidentally put the Webkit repo (~1m files) into Dropbox once and it didn't go well. Git needs a consistent view of the filesystem across many files to work, and that's not really possible with that many files stored in a sync system that works per-file like Drive does. I put Git in the category of specialist software that shouldn't be operated in Drive. By all means tar and backup, that should be effective, but there's no need to store all the individual files.