How can I get a list of all repositories and PPAs from the command line into an install script?

I know how to list all packages installed on my system.

But how could I get a list of all repositories and PPA's into a script that I can run on a new machine to replicate the repository setup including the keys?

I know I can look into /etc/apt/sources.list and /etc/apt/sources.list.d, but I'm looking for a way to generate a script that executes all apt-add-repository commands on a new system (that sorts out getting all keys).

Any ideas?

Thanks for the pointers. With a little cleanup I got a script that lists the PPAs, but not any other repository:

#! /bin/sh
# listppa Script to get all the PPA installed on a system ready to share for reininstall
for APT in `find /etc/apt/ -name \*.list`; do
    grep -o "^deb http://ppa.launchpad.net/[a-z0-9\-]\+/[a-z0-9\-]\+" $APT | while read ENTRY ; do
        USER=`echo $ENTRY | cut -d/ -f4`
        PPA=`echo $ENTRY | cut -d/ -f5`
        echo sudo apt-add-repository ppa:$USER/$PPA
    done
done

When you call it with listppa > installppa.sh you get a script you can copy on a new machine to reinstall all PPA.

Next stop: do that for the other repositories:

#! /bin/sh
# Script to get all the PPA installed on a system
for APT in `find /etc/apt/ -name \*.list`; do
    grep -Po "(?<=^deb\s).*?(?=#|$)" $APT | while read ENTRY ; do
        HOST=`echo $ENTRY | cut -d/ -f3`
        USER=`echo $ENTRY | cut -d/ -f4`
        PPA=`echo $ENTRY | cut -d/ -f5`
        #echo sudo apt-add-repository ppa:$USER/$PPA
        if [ "ppa.launchpad.net" = "$HOST" ]; then
            echo sudo apt-add-repository ppa:$USER/$PPA
        else
            echo sudo apt-add-repository \'${ENTRY}\'
        fi
    done
done

This should do the trick. I needed a question on superuser to figure out the correct regex.