[rancid] change email diff subject line : $Group/$Device router config diffs

[Shaun Krok]

Hi

I know this probably has been queried  and resolved before but I am 
struggling to make rancid
include $Group/$Device in the subject line.

I know this works when using -r command line option but this works only 
for a single host (from router.db)

any help with this would be much appreciated !

running version 3.1

Shaun