-echo "Running diff: $old -> $new"
-LC_ALL=C svn diff --old=$old --new=$new > lighttpd-branch.diff.tmp
+echo >&2 "Running diff: $old -> $new"
+LC_ALL=C svn diff --old=$old --new=$new > $out.tmp
+revno=$(sed -ne 's,^[-+]\{3\} .*\t(revision \([0-9]\+\))$,\1,p' $out.tmp | sort -urn | head -n1)
+echo >&2 "Revision $revno"
+[ "$revno" -gt 0 ] || exit 1
+
+sed -i -e "1i# Revision $revno" $out.tmp
+filter < $out.tmp > $out.tmp2 && mv -f $out.{tmp2,tmp}
+
+if cmp -s $out{,.tmp}; then
+ echo >&2 "No new diffs..."
+ rm -f $out.tmp
+ exit 0
+fi
+mv -f $out{.tmp,}