The correct api is trace_printf_key(), not trace_print_key().
Also do not throw a random string at printf(3)-like function;
instead, feed it as a parameter that is fed to a "%s" conversion
specifier.
Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>