Allow state pull to pass any options

At time of writing, there is no valid option in Terraform v0.12/v0.13.
It's a room for future extensions not to break the interface.

tfexec/terraform.go

@@ -78,7 +78,7 @@ type TerraformCLI interface {
 	StateList(ctx context.Context, state *State, addresses []string, opts ...string) ([]string, error)
 
 	// StatePull returns the current tfstate from remote.
-	StatePull(ctx context.Context) (*State, error)
+	StatePull(ctx context.Context, opts ...string) (*State, error)
 
 	// StatePush pushs a given State to remote.
 	StatePush(ctx context.Context, state *State) error

tfexec/terraform_state_pull.go

@@ -3,8 +3,13 @@ package tfexec
 import "context"
 
 // StatePull returns the current tfstate from remote.
-func (c *terraformCLI) StatePull(ctx context.Context) (*State, error) {
-	stdout, _, err := c.Run(ctx, "state", "pull")
+func (c *terraformCLI) StatePull(ctx context.Context, opts ...string) (*State, error) {
+	args := []string{"state", "pull"}
+	// At time of writing, there is no valid option in Terraform v0.12/v0.13.
+	// It's a room for future extensions not to break the interface.
+	args = append(args, opts...)
+
+	stdout, _, err := c.Run(ctx, args...)
 	if err != nil {
 		return nil, err
 	}

tfexec/terraform_state_pull_test.go

@@ -19,6 +19,7 @@ func TestTerraformCLIStatePull(t *testing.T) {
 	cases := []struct {
 		desc         string
 		mockCommands []*mockCommand
+		opts         []string
 		want         *State
 		ok           bool
 	}{
@@ -45,13 +46,26 @@ func TestTerraformCLIStatePull(t *testing.T) {
 			want: nil,
 			ok:   false,
 		},
+		{
+			desc: "with opts", // there is no valid option for now, just pass a dummy for testing.
+			mockCommands: []*mockCommand{
+				{
+					args:     []string{"terraform", "state", "pull", "-foo"},
+					stdout:   stdout,
+					exitCode: 0,
+				},
+			},
+			opts: []string{"-foo"},
+			want: NewState([]byte(stdout)),
+			ok:   true,
+		},
 	}
 
 	for _, tc := range cases {
 		t.Run(tc.desc, func(t *testing.T) {
 			e := NewMockExecutor(tc.mockCommands)
 			terraformCLI := NewTerraformCLI(e)
-			got, err := terraformCLI.StatePull(context.Background())
+			got, err := terraformCLI.StatePull(context.Background(), tc.opts...)
 			if tc.ok && err != nil {
 				t.Fatalf("unexpected err: %s", err)
 			}