Mergemaster on a distant system

[ptitoliv]

Hello everybody,

I would like to upgrade one of my FreeBSD boxes but I have a little 
problem with the mergemaster. It is said in the handbook that is 
necessary to reboot on single mode in order to modify config file using 
mergemaster. But the problem is that the box concerned is not physically 
accessible (only with SSH). So what are the possibles solutions in order 
to upgrade my FreeBSD in a clean way ?

Thank you for your answers.

Best Regards,
Ptitoliv