--- /dev/null
+#!/bin/sh
+# stamp the source with the originating git revision.
+git_rev=$(git show --pretty'=oneline' 'HEAD' | head -n1 | cut -f1 -d' ')
+#git_r='assign("git_revision","'$git_rev'",envir=.GlobalEnv)'
+git_r=' global("git_revision","'$git_rev'")'
+
+awk -v "git_r=$git_r" '
+/# git_revision }/ {suppress=0}
+suppress == 0 {print}
+/# git_revision {/ {print git_r; suppress=1}
+' <R/zzz.R >R/zzz.R.new && \
+mv R/zzz.R.new R/zzz.R