Adjusted the description, I think there's a potential problem than can handled better from user perspective.
The proposed branch adds upgrade) preinst rule for resolvconf < 1.64, and creates the symlink if and only if /etc/resolv.conf does not exist at all (normal file or symlink). I've tested that it does nothing when upgrading from newer resolvconf, and also leaves /etc/resolv.conf untouched if it exists as a normal file or a symlink, when upgrading from the precise version. It fixes the issue I saw on upgrade.
Adjusted the description, I think there's a potential problem than can handled better from user perspective.
The proposed branch adds upgrade) preinst rule for resolvconf < 1.64, and creates the symlink if and only if /etc/resolv.conf does not exist at all (normal file or symlink). I've tested that it does nothing when upgrading from newer resolvconf, and also leaves /etc/resolv.conf untouched if it exists as a normal file or a symlink, when upgrading from the precise version. It fixes the issue I saw on upgrade.