In this article, I will show you how you can update a project, that was created from a copier template. In my previous article, we learnt how we can create a project template. I listed the only reason I choose to use copier over say cookiecutter was that it provided an “easy” way to update downstream projects.

Existing Repository From here on out we will assume you have a template repository that uses copier. Here is an example repository.



Some terminology:

  • Template Repository: The repository is built using copier. This is the repository which we use to create projects.
  • Downstream Project: A project created using the template repository. This is the project we will deploy into production.

To be able to use copier update to update a downstream project we need to meet the following conditions:

  • The template includes a valid .copier-answers.yml file.
  • The template is versioned with Git (with tags).
  • The downstream project is versioned with Git.

In this example we will assume these URLs:

Change a file

So let’s pretend we have a template repository, and we make an update to it. Say we add a new make target like so:


.PHONY: help
help: ## Generates a help README
	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'

Now rather than copy this manually to each of our downstream projects/ We can automate this process a bit. So first things first, we need to commit this change on the template repository and then create a new git tag. This is the recommended way to version the templates repository. i.e. git tag 0.3.1 and then you can do git push --tags. To publish the tags on your remote repository.

As a slight aside I also keep track of my changes in a using keepachangelog format. Which directly relates to git tags.

Updating downstream project

Once we have published and tagged the change say with 0.3.1. The change is now ready to be pulled in from our downstream projects. Now let’s go to our downstream project. Assume the .copier-answers.yml looks something like this:

# Changes here will be overwritten by Copier
_commit: 0.3.0
_src_path: gl:banter-bus/fastapi-template

We can run copier update and it should pull in the latest changes to the makefile in our project. It will also update the _commit: 0.3.1. This is how we keep track of what version of the template this project is currently using. You shouldn’t update this file.

If you need to install copier you can read how to do it here.

More Details If you want more specifics about how copier does its update you can read about it here.

That’s It!

So that’s it! We looked at how we can update our downstream projects when we use copier to template our repository. One other thing we could look at doing is trying to automate this further, perhaps by automatically creating PR/MRs, to all downstream projects when we update thte template. We would run copier update and create a new branch, that a human could then review. A bit like dependabot for dependencies in GitHub.