I also found this in the README.gz located in /usr/share/doc/resolvconf on Ubuntu 14.04. It provides a bit more clarity.
Beware of the resolv.conf file being managed by the service resolvconf.
dns-search appears to be a necessary line in the stanza of a logical interface.
* Remove any "up" or "down" commands from /etc/network/interfaces
that futz with /etc/resolv.conf and remove any scripts from
/etc/network/if-*.d/ that futz with /etc/resolv.conf.
* For each inet static logical interface through which a nameserver is
accessible, add lines like the following to /etc/network/interfaces .
dns-nameservers 18.104.22.168 22.214.171.124
dns-search foo.org bar.com
Other recognized option words are 'dns-domain' and 'dns-sortlist'.
These option names correspond to the option names used in the
resolv.conf file with one exception: whereas one lists several
nameserver addresses in /etc/resolv.conf on several "nameserver"
lines, here one should list them all on a single "dns-nameservers"
line. See resolv.conf(5) for more information. The lines entered
in /etc/network/interfaces will be added to the resolver
configuration file (without the "dns-" prefix, of course) when a
physical interface is brought up as that logical interface.
Note that the resolver configuration is updated AFTER all the "up"
commands have been run; therefore "up" commands cannot make use of
nameservers listed on "dns-nameservers" lines in the same logical
interface stanza. Changing this will require modifying ifupdown
so that it talks to resolvconf; currently resolvconf hooks into
ifupdown using the script /etc/network/if-up.d/000resolvconf. Note
too that scripts in /etc/network/if-up.d/ CAN make use of the
added nameservers because those scripts run after 000resolvconf.