Fix ref log parsing so it works properly.

The log parser was only ever matching the last log record due to
calling strtoul on "> 1136091609" rather than " 1136091609".  Also
once a match for '@' has been found after the name of the ref there
is no point in looking for another '@' within the remaining text.

Signed-off-by: Junio C Hamano <junkio@cox.net>