first commit

cli/internal/update/replace_windows.go

@@ -0,0 +1,29 @@
+//go:build windows
+
+package update
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// atomicReplace replaces oldPath with newPath. On Windows, we cannot rename
+// over a running executable directly, so we move the old binary aside first.
+func atomicReplace(oldPath, newPath string) error {
+	backupPath := filepath.Join(filepath.Dir(oldPath), ".bifrost-old.exe")
+	os.Remove(backupPath) // clean up any previous backup
+
+	if err := os.Rename(oldPath, backupPath); err != nil {
+		return err
+	}
+	if err := os.Rename(newPath, oldPath); err != nil {
+		// Rollback — report if rollback also fails
+		if rbErr := os.Rename(backupPath, oldPath); rbErr != nil {
+			return fmt.Errorf("rename failed: %w; rollback also failed: %v (backup at %s)", err, rbErr, backupPath)
+		}
+		return err
+	}
+	os.Remove(backupPath)
+	return nil
+}