diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 00000000..31ba80b2
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "doc/tools/gitwash"]
+	path = doc/tools/gitwash
+	url = git@github.com:matthew-brett/gitwash.git
diff --git a/doc/tools/gitwash b/doc/tools/gitwash
new file mode 160000
index 00000000..06d130ab
--- /dev/null
+++ b/doc/tools/gitwash
@@ -0,0 +1 @@
+Subproject commit 06d130ab98d78e5a831b32a6624cad2bc481cacd