Use just as a Git Pre-Commit Hook

Introduction

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As a fan of make-like tools such as just or Task and appreciating the guardrails provided by Git pre-commit, I dislike the redundancy of having to define commands like linting both in the justfile/taskfile as well as in the .pre-commit-config.yaml. To solve this, I’ve built a simple Git-native pre-commit hook which only delegates to a just recipe (in our case called lint) where all the checks are defined. While the following examples use just, they are easily adaptable to Task or even good old make.

Define just Recipe

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As a prerequisite, we need a justfile which contains all the checks we expect to pass (meaning the commands results in a 0 return code), before a new Git commit can be created. For a Python codebase this could look like this:

lint:
    just --fmt --unstable --check
    uvx ruff check
    uvx ruff format --check

Set Up Pre-commit Hook

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Within your repository, create a new file for the pre-commit hook using the editor of your choice. For VS Code, run

touch .git/hooks/pre-commit

The pre-commit file should then have the following content.

#!/bin/sh

# Prevent commit if 'just lint' recipe fails.
if ! just lint; then
    echo "Pre-commit check failed!"
    exit 1
fi

Finally, set the permissions such that the hook can be executed.

chmod u+x .git/hooks/pre-commit

Enable/Disable Hook

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To disable the git hook, remove the permission to execute the script.

chmod u-x .git/hooks/pre-commit

Consequently, to re-enable the hook, add the permission again.

chmod u+x .git/hooks/pre-commit

Bonus: Putting Everything in a justfile

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To not set up the pre-commit hook manually, you can also do this via a enable-pre-commit recipe.

lint:
    just --fmt --unstable --check
    uvx ruff check
    uvx ruff format --check

@enable-pre-commit:
    echo '#!/bin/sh\n\n# Prevent commit if '\''just lint'\'' recipe fails.\nif ! just lint; then\n    echo "Pre-commit check failed!"\n    exit 1\nfi' > .git/hooks/pre-commit
    chmod u+x .git/hooks/pre-commit
    @echo "Pre-commit hook enabled."

@disable-pre-commit:
    chmod u-x .git/hooks/pre-commit
    @echo "Pre-commit hook disabled."