Let Tarrastate take care of workspaces

[PierreKerschgens]

What about (optional) storing the preferred workspace in the given var file and let terrastate do the workspace selection.

You could append this variable to env/dev.tfvars:
state_workspace = "dev"

Then instead of using:
terraform workspace select dev
terraform plan -var-file=env/dev.tfvars

Use (requires implementation of #2):
terrastate plan -var-file=env/dev.tfvars

[janritter]

Terrastate should eliminate the need for workspaces, instead different keys should be use