Memory allocated to the fields of msg by get_message() isn't freed.
This is potentially a big leak, because fresh memory is allocated to
store the commit message for each commit. Fix this using
free_message().
Reported-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>