Package exec is glue between the vendored terraform codebase and installer.

Apply unpacks the platform-specific Terraform modules into the given directory and then runs 'terraform init' and 'terraform apply'.

Destroy unpacks the platform-specific Terraform modules into the given directory and then runs 'terraform init' and 'terraform destroy'.

StateFileName is the default name for Terraform state files.

VarFileName is the default name for Terraform var file.