How to upgrade dreamfactory droplet on digitalocean?

I have a dreamfactory droplet which is running on DigitalOcean. I am trying to upgrade its dreamfactory version from current DreamFactory Version: 2.0.4 to latest.
I tried following steps mentioned in upgrade section of dreamfactory installation guide here:
But while trying to run any Git command I get this error:

fatal: Not a git repository (or any of the parent directories): .git

Is there any particular way to update it?