store: local store

This just returns the verbatim string.

store.go

@@ -12,6 +12,12 @@ type Store interface {
 	fmt.Stringer
 }
 
+// Local points to a local filesystem path containing a nix store.
+type Local string
+
+func (Local) Environ() []string    { return nil }
+func (store Local) String() string { return string(store) }
+
 const (
 	EnvAwsSharedCredentialsFile = "AWS_SHARED_CREDENTIALS_FILE"
 )

store_test.go

@@ -6,6 +6,16 @@ import (
 	"gensokyo.uk/nix"
 )
 
+func TestLocal(t *testing.T) {
+	if got := nix.Local("/").String(); got != "/" {
+		t.Errorf("String: %v, want %v", got, "/")
+	}
+
+	if got := nix.Local("").Environ(); got != nil {
+		t.Errorf("Environ: %v, want %v", got, nil)
+	}
+}
+
 func TestBinaryCache(t *testing.T) {
 	testCases := []struct {
 		name    string