add install commands

internal/installer/helpers.go

@@ -0,0 +1,40 @@
+package installer
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+)
+
+func copySelfAtomic(src, dst string, mode os.FileMode) error {
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+
+	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
+		return err
+	}
+
+	tmp := dst + ".tmp"
+	out, err := os.OpenFile(tmp, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, mode)
+	if err != nil {
+		return err
+	}
+	_, copyErr := io.Copy(out, in)
+	closeErr := out.Close()
+	if copyErr != nil {
+		_ = os.Remove(tmp)
+		return copyErr
+	}
+	if closeErr != nil {
+		_ = os.Remove(tmp)
+		return closeErr
+	}
+	if err := os.Rename(tmp, dst); err != nil {
+		_ = os.Remove(tmp)
+		return err
+	}
+	return nil
+}