write changelog from git

gistfile1.txt

#!/bin/bash
OLD=HEAD
for I in $(git tag  | perl -e 'print join "\n", reverse <STDIN>')
do
  if
    [ "x$OLD" == "x$I" ]
  then
    echo "Changelog"
  else
    git log -n1 --format="$OLD -- %aD" $OLD
    git --no-pager log --format='  %h %aN <%aE> %s'  $OLD ^$I
    OLD=$I
fi
done > Changes