Git: moving a module into a monorepo

My team has a repo where we keep all our terraform modules, but we had a separate module off in its own repo for reasons that are no longer relevant.

Let’s call the modules repo The module moving into it, let’s call it, because it’s a postgres module.

First, clone both repos.:

git clone
git clone

I can’t just add postgres-module as a remote to our-modules and pull from it, because I need the files to end up in a subdirectory of our-modules. Instead, I have to make a commit to postgres-module that puts its files in exactly the place that I want them to land in our-modules. If I didn’t, the files from both repos would hit a merge conflict.

So, here’s how to make that one last commit:

cd postgres-module
mkdir postgres
git mv *.tf postgres/
git mv *.md postgres/
git commit -m "postgres: prepare for move to modules repo"
cd ..

Notice that I don’t push that commit anywhere. It just sits on my filesystem, because I’ll pull from that part of my filesystem instead of across the network to get the repo’s changes into the modules repo:

cd our-modules
git remote add pg ../postgres-module/
git pull pg master --allow-unrelated-histories
git remote rm pg
cd ..

At this point, I have all the files and their history from the postgres module in the postgres directory of the our-modules repo. I can then follow the usual process to PR these changes to the our-modules remote:

cd our-modules
git checkout -b import-pg-module
git push origin import-pg-module

We eventually ended up to skip importing the history on this module, but figuring out how to do it properly was still an educational exercise.