Adding copyright notices and minor colateral cleanup.

Author: rwgk

CMakeLists.txt

@@ -106,6 +106,7 @@ set(PYBIND11_HEADERS
     include/pybind11/detail/init.h
     include/pybind11/detail/internals.h
     include/pybind11/detail/smart_holder_poc.h
+    include/pybind11/detail/smart_holder_sfinae_hooks_only.h
     include/pybind11/detail/smart_holder_type_casters.h
     include/pybind11/detail/typeid.h
     include/pybind11/attr.h

include/pybind11/detail/smart_holder_sfinae_hooks_only.h

@@ -1,3 +1,7 @@
+// Copyright (c) 2021 The Pybind Development Team.
+// All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
 #pragma once
 
 #include "common.h"

include/pybind11/detail/smart_holder_type_casters.h

@@ -1,5 +1,8 @@
+// Copyright (c) 2021 The Pybind Development Team.
+// All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
 #pragma once
-#define PYBIND11_SMART_HOLDER_TYPE_CASTERS_H_IS_INCLUDED
 
 #include "smart_holder_poc.h"
 #include "smart_holder_sfinae_hooks_only.h"

tests/extra_python_package/test_files.py

@@ -44,6 +44,7 @@
     "include/pybind11/detail/init.h",
     "include/pybind11/detail/internals.h",
     "include/pybind11/detail/smart_holder_poc.h",
+    "include/pybind11/detail/smart_holder_sfinae_hooks_only.h",
     "include/pybind11/detail/smart_holder_type_casters.h",
     "include/pybind11/detail/typeid.h",
 }