Reported by Tony Cooper, Jan 14, 2011

$mtn = Monotone::AutomateStdio->new("my-db.mtn");
Attempts to open "/my-db.mtn".

The mtn subprocess is started under / when given a db file name so 
as to help avoid workspace interference (even when the relevant 
--no-workspace switch, or what ever it is, wasn't supported). Need 
to obtain the canonical absolute path to the db before doing a 
chdir("/").