Set emacs -nw as default editor
Create a script that starts emacs with -nw flag, e.g. /usr/local/bin/emacs-nw.
#!/bin/sh
emacs -nw "$@"
Install it with update-alternatives --install.
sudo update-alternatives --install /usr/bin/editor editor /usr/local/bin/emacs-nw 2
Configure editor to be your new script.
sudo update-alternatives --set editor /usr/local/bin/emacs-nw
Add the following to your ~/.bashrc
file (or the config file for your shell if it is not Bash).
export EDITOR="emacs -nw"
This should set (and export) an env variable setting your default editor as Emacs in non-graphical mode.