It was observed that the variable '$displaypath' was accessible but
undocumented. Hence, document it.
Discussed-with: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Stefan Beller <sbeller@google.com> Signed-off-by: Prathamesh Chavan <pc44800@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>