feat(cli): add transactional installation backups

tools/tht/internal/lifecycle/lock_test.go

@@ -0,0 +1,50 @@
+package lifecycle
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/aritmolab/thothii/tools/tht/internal/config"
+)
+
+func TestLifecycleLockIsExclusivePerInstallationAndReusableAfterRelease(t *testing.T) {
+	installation := config.Installation{ProjectDirectory: t.TempDir(), Path: filepath.Join(t.TempDir(), "thothii-installation.yaml")}
+	first, err := Acquire(installation)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = first.Release() })
+
+	if _, err := Acquire(installation); !errors.Is(err, ErrLocked) {
+		t.Fatalf("second Acquire() error = %v, want ErrLocked", err)
+	}
+	if err := first.Release(); err != nil {
+		t.Fatal(err)
+	}
+	second, err := Acquire(installation)
+	if err != nil {
+		t.Fatalf("Acquire() after release: %v", err)
+	}
+	if err := second.Release(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestLifecycleLockReleaseDoesNotRemoveAnotherOwnersFile(t *testing.T) {
+	installation := config.Installation{ProjectDirectory: t.TempDir(), Path: filepath.Join(t.TempDir(), "thothii-installation.yaml")}
+	lock, err := Acquire(installation)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(lock.Path(), []byte(`{"token":"different-owner"}`), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := lock.Release(); !errors.Is(err, ErrOwnership) {
+		t.Fatalf("Release() error = %v, want ErrOwnership", err)
+	}
+	if _, err := os.Stat(lock.Path()); err != nil {
+		t.Fatalf("foreign lock was removed: %v", err)
+	}
+}