rtrfilter can be used to filter rancid diffs to avoid sending unwanted
diffs to certain recipient(s) or diffs which those recipient(s) should
not see without the need to create separate or duplicate group(s).

/etc/aliases eg:

rancid-foo:	engineering,
		customer-ops-foo
#
# only send diffs for the SJC routers (aka. *.sjc.shrubbery.net)
customer-ops-foo:	"| /home/rancid/util/rtrfilter -i '\.sjc\.' -s 'sjc router diffs' customer-ops"
#
customer-ops:	jimbob,
		sally