This script will add all submodules from just a .gitmodules file

addsubmodules.sh

#!/bin/sh
# This script will add all submodules from just a .gitmodules file
#
# This script copied from https://www.willhallonline.co.uk/blog/2019-03-05-scripting-adding-gitmodules/
# One addition is the '--force' directive on 'submodule add'.

set -e

git config -f .gitmodules --get-regexp '^submodule\..*\.path$' |
    while read path_key path
    do
        url_key=$(echo $path_key | sed 's/\.path/.url/')
        url=$(git config -f .gitmodules --get "$url_key")
        git submodule add --force $url $path
    done