Having cron-apt choose the default action (rather than yes) during upgrades?

[Rich Stanton <stantonrj@Cf.ac.uk>]

I want to use cron-apt to auto install updates overnight.  I'm aware of
the reasons against doing this, and am prepared to live with the
consequences on this occasion.  I assume I can just create a file in
/etc/cron-apt/action.d called 9-install & put the command 'dist-upgrade
-y' in there.  However I don't necessarily want it to default to 'yes'
on every question - during a manual upgrade, if a config file has been
modified from the default, the default is to not overwrite it.  I'd like
cron-apt to do the default in this case, which is 'no' (don't
overwrite).  Will the -y action say yes, or will it do the default
action (no in this case)?  If it says 'yes' how do I make it do the
default action?

Thanks!