unlock|close|commit_ref can be made static since there are no more external
callers.
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com> Signed-off-by: Stefan Beller <sbeller@google.com> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>