anna uses a retriever to download udebs, checks their consistency, and
calls udpkg to install them. It can be called as follows:
Use the given retriever, get the list of all udebs it can
retrieve, work out which to install by default, prompt the user
for which to install, and install all selected.
anna <retriever> default
Same as above, except that the retriever is stored as the default
retriever to use.
anna install <udeb ..>
Uses the default retriever to get the specified udebs and installs
them. Dependencies will automatically be installed too. Note that
this still needs a debconf frontend to be running, so use of the
anna-install command in debian-installer-utils is better for