We forgot to free defmsg when returning early for a fast-forward.
Fixing this should reduce noise during test suite runs with valgrind.
More importantly, once cherry-pick learns to pick multiple commits,
the amount of memory leaked would start to add up.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>