Why mysqldump instead of using the binary log? Just dump the result of SHOW MASTER STATUS to a text file in your git directory, back up your binary log files on a regular basis, and then you just use the stop position feature of the binlog utility[1] to restore to that point in time from the binary logs. A lot faster than doing mysqldump and a lot less likely to lock tables or slow down your database.

[1] http://dev.mysql.com/doc/refman/5.0/en/point-in-time-recover...