Pre-commit tools

Pre-commit tools run a configurable number of checks every time you want to commit some code. Their purpose is to catch some easily avoidable errors, such as linting or styling errors, before they are pushed to a branch. The two main pre-commit tools are pre-commit and prek. Jarl provides a pre-commit hook that works with both of these tools: jarl-pre-commit.

pre-commit

Use this in .pre-commit-config.yaml:

repos:
-   repo: https://github.com/etiennebacher/jarl-pre-commit
    rev: 0.4.0
    hooks:
      - id: jarl-check

prek

prek can read .pre-commit-config.yaml but also has its own format, prek.toml.

Use this in prek.toml:

[[repos]]
repo = "https://github.com/etiennebacher/jarl-pre-commit"
rev = "0.4.0"
hooks = [
  { id = "jarl-check" },
]

Choosing the version of Jarl to use

The rev parameter determines the version of Jarl to use. Starting from 0.4.0, all releases of Jarl have a matching release in jarl-pre-commit (see jarl-pre-commit tags).

When you call pre-commit or prek, it fetches the corresponding Jarl binary and caches it in ~/.cache/jarl-pre-commit (for instance ~/.cache/jarl-pre-commit/jarl-0.4.0). This implies two things:

• you may have projects with pre-commit config files that use different versions of Jarl;
• the version of Jarl on the $PATH is not affected, meaning that projects that don’t use pre-commit are not affected by the version of Jarl used in a project with pre-commit.