If ever use Google Docs, there is a complete revision history of all changes made to the doc. Neutron Drive implements this feature and keeps revisions for you also of any file you edit.

If you ever need to go back and revert to an old version of a file you can just review all your old versions and revert.

All files have revisions management in Google Drive. You can see this feature by doing: Right click on a file > Manage revisions...

Then it's up to the client using the Drive API to use the correct parameter when uploading a new change to create a new revision or overwrite the current revision.