Merging repos into a monorepo

mono-repo.sh

# SRC_REPO, TGT_REPO are relative to current directory

SRC_REPO=$1
TGT_REPO=$2
DIR_NAME=$3
BRANCH_NAME=$4

pushd $SRC_REPO
git filter-repo --to-subdirectory "$DIR_NAME" # replace w/ your dir name
popd

pushd $TGT_REPO
git config pull.rebase false # make sure this is set
git remote add $BRANCH_NAME ../$SRC_REPO # 
git pull $BRANCH_NAME main --allow-unrelated-histories
git remote rm $BRANCH_NAME

You have to install git filter-repo