Add a dummy common.h header with a deprecation warning
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2a3e1ed..4280ba7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -51,6 +51,7 @@
   include/pybind11/buffer_info.h
   include/pybind11/cast.h
   include/pybind11/chrono.h
+  include/pybind11/common.h
   include/pybind11/complex.h
   include/pybind11/options.h
   include/pybind11/eigen.h
diff --git a/include/pybind11/common.h b/include/pybind11/common.h
new file mode 100644
index 0000000..6c8a4f1
--- /dev/null
+++ b/include/pybind11/common.h
@@ -0,0 +1,2 @@
+#include "detail/common.h"
+#warning "Including 'common.h' is deprecated. It will be removed in v3.0. Use 'pybind11.h'."
diff --git a/setup.py b/setup.py
index e24f34b..b761205 100644
--- a/setup.py
+++ b/setup.py
@@ -23,6 +23,7 @@
         'include/pybind11/buffer_info.h',
         'include/pybind11/cast.h',
         'include/pybind11/chrono.h',
+        'include/pybind11/common.h',
         'include/pybind11/complex.h',
         'include/pybind11/eigen.h',
         'include/pybind11/embed.h',