automake: Add git-version-gen to EXTRA_DIST and add .tarball-version hook
diff --git a/Makefile.am b/Makefile.am
index 12940a1..5ca15d0 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -3,4 +3,8 @@
 SUBDIRS = src include tools docs
 
 EXTRA_DIST = \
-	README.md
+	README.md \
+	git-version-gen
+
+dist-hook:
+	echo $(VERSION) > $(distdir)/.tarball-version