1 files changed, 23 insertions, 0 deletions
diff --git a/third_party/nix/src/nix/legacy.hh b/third_party/nix/src/nix/legacy.hh
new file mode 100644
index 0000000000..a0fc88da24
--- /dev/null
+++ b/third_party/nix/src/nix/legacy.hh
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <functional>
+#include <map>
+#include <string>
+
+namespace nix {
+
+typedef std::function<void(int, char**)> MainFunction;
+
+struct RegisterLegacyCommand {
+  using Commands = std::map<std::string, MainFunction>;
+  static Commands* commands;
+
+  RegisterLegacyCommand(const std::string& name, MainFunction fun) {
+    if (!commands) {
+      commands = new Commands;
+    }
+    (*commands)[name] = fun;
+  }
+};
+
+}  // namespace nix