This question brought me to another question: is there any VCS/tool for a VCS which automatically backups your source code between the last checkout and current changes?

I had the problem of loosing uncommited source code changes just one week ago.
I did not want to commit yet because the changes were incomplete. But then, an error when moving the data to an USB stick caused the data loss.

That's the opposite what a cloud service (like Google Drive, SkyDrive, DropBox, ...) does: it tracks each change you made!
Have you lost your data? That's no problem because you have the latest version online.

So what would a combined solution look like?
It would offer full functionality of a VCS including auto-syncing of any intermediate changes between two commits/checkouts to a temporary online location.