Include a remove-apt-repository ?

Here is more information:

sudo add-apt-repository --help
sudo: unable to resolve host new-host-2
Usage: add-apt-repository <sourceline>

add-apt-repository is a script for adding apt sources.list entries.
It can be used to add any repository and also provides a shorthand
syntax for adding a Launchpad PPA (Personal Package Archive)
repository.

<sourceline> - The apt repository source line to add. This is one of:
  a complete apt line in quotes,
  a repo url and areas in quotes (areas defaults to 'main')
  a PPA shortcut.
  a distro component

  Examples:
    apt-add-repository 'deb http://myserver/path/to/repo stable myrepo'
    apt-add-repository 'http://myserver/path/to/repo myrepo'
    apt-add-repository 'https://packages.medibuntu.org free non-free'
    apt-add-repository http://extras.ubuntu.com/ubuntu
    apt-add-repository ppa:user/repository
    apt-add-repository multiverse

If --remove is given the tool will remove the given sourceline from your
sources.list

Options:
  -h, --help show this help message and exit
  -m, --massive-debug Print a lot of debug information to the command line
  -r, --remove remove repository from sources.list.d directory
  -k KEYSERVER, --keyserver=KEYSERVER
                        URL of keyserver. Default:
                        hkp://keyserver.ubuntu.com:80/
  -y, --yes Assume yes to all queries

You can use the add-apt-repository in combination with the following command

find /etc/apt -name '*.list' -exec bash -c 'echo -e "\n$1\n"; cat -n "$1"' _ '{}' \;

to determine which repositories you want to delete.

Your arguments are valid and so I suggest contacting Chow Loong Jin <email address hidden>

I hope Chow Loong Jin is still working on it.