Updating a project

Copier has an "update" feature. It means that, once a project is generated, you can keep updating it with the latest changes that happen in the template.

It's particularly useful when you manage a lot of projects, all generated from the same template, and you want to apply a change to all your projects.

Example: the template fixed a bug in the Makefile. You don't want to apply it manually to your projects.

To update your project, go into its directory, and run copier update. Your repository must be clean (no modified files) when running this command.

Copier will use the previous answers you gave when generating the project, to re-generate it in a temporary directory, compare the two versions, and apply patches to your documents. When it's not sure, or when there's a conflict, it will ask you if you want to skip that change or force it. Your previous answers are stored in the .copier-answers.yml file at the root of the project directory:

📁 my-project
├── 📄 .copier-answers.yml
└── 📄 etc.

And the file looks like this:

# Changes here will be overwritten by Copier
_commit: 0.1.10
_src_path: gh:pawamoy/copier-pdm
author_email: pawamoy@pm.me
author_fullname: "Timothée Mazzucotelli"
author_username: pawamoy
copyright_date: '2020'
copyright_holder: "Timothée Mazzucotelli"
copyright_holder_email: pawamoy@pm.me
copyright_license: ISC License
project_description: Automatic documentation from sources, for MkDocs.
project_name: mkdocstrings
python_package_command_line_name: ""
python_package_distribution_name: mkdocstrings
python_package_import_name: mkdocstrings
repository_name: mkdocstrings
repository_namespace: pawamoy
repository_provider: github.com

If you want to use all previous answers without copier prompting you for each answer, run copier update --force.

Since we are generally using Git in our projects, my recommendation is to not think at all and blindly apply every change Copier proposes. Indeed, you'll be able to see the diff with git diff, un-apply changes on whole files with git checkout -- FILE if they are not relevant, or do partial, interactive commits with git add -p or within your IDE interface (PyCharm and VSCode have good support and UX for selecting and committing changes).