move VarEnvPrefix out of terraform pkg

command/meta_vars.go

@@ -15,6 +15,10 @@ import (
 	"github.com/hashicorp/terraform/tfdiags"
 )
 
+// VarEnvPrefix is the prefix for environment variables that represent values
+// for root module input variables.
+const VarEnvPrefix = "TF_VAR_"
+
 // collectVariableValues inspects the various places that root module input variable
 // values can come from and constructs a map ready to be passed to the
 // backend as part of a backend.Operation.
@@ -31,10 +35,10 @@ func (m *Meta) collectVariableValues() (map[string]backend.UnparsedVariableValue
 	{
 		env := os.Environ()
 		for _, raw := range env {
-			if !strings.HasPrefix(raw, terraform.VarEnvPrefix) {
+			if !strings.HasPrefix(raw, VarEnvPrefix) {
 				continue
 			}
-			raw = raw[len(terraform.VarEnvPrefix):] // trim the prefix
+			raw = raw[len(VarEnvPrefix):] // trim the prefix
 
 			eq := strings.Index(raw, "=")
 			if eq == -1 {

terraform/interpolate.go

@@ -16,12 +16,6 @@ import (
 	"github.com/hashicorp/terraform/flatmap"
 )
 
-const (
-	// VarEnvPrefix is the prefix of variables that are read from
-	// the environment to set variables here.
-	VarEnvPrefix = "TF_VAR_"
-)
-
 // Interpolater is the structure responsible for determining the values
 // for interpolations such as `aws_instance.foo.bar`.
 type Interpolater struct {