add git-version-gen to auto-generate git based version number
diff --git a/Makefile.am b/Makefile.am
index 13cec6c..491e1ff 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,3 +1,11 @@
+AUTOMAKE_OPTIONS = foreign dist-bzip2
+
 SUBDIRS = src
 
-EXTRA_DIST = asn1
+EXTRA_DIST = asn1 .version
+
+BUILT_SOURCES = $(top_srcdir)/.version
+$(top_srcdir)/.version:
+	echo $(VERSION) > $@-t && mv $@-t $@
+dist-hook:
+	echo $(VERSION) > $(distdir)/.tarball-version