Some people in #linux-rt noticed that describing what "--mirror" option does
with "it mirrors" is way insufficient.
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Darren 'Some People' Hart <darren@dvhart.com>
Cc: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>