precommit

Precommit refers to a hook mechanism that runs automatically before a commit is created in a version control system, most commonly Git. A pre-commit hook is a script or program that checks new changes for quality, style, or correctness and can abort the commit if issues are found. Typical checks include code formatting, linting, unit tests, or ensuring certain files are present or in a specific state. By intercepting commits early, precommit processes aim to keep repository quality consistent and reduce regressions.

In Git, hooks are executable scripts located in the .git/hooks directory of a repository. Pre-commit hooks are run after the user initiates a commit and before the commit is finalized. These hooks can be locally authored or provided by external tools. Traditionally, each project maintains its own set of pre-commit scripts, which are not versioned unless placed under version control alongside the project.

A popular tool for managing pre-commit checks is the pre-commit framework. This framework allows teams to define a configuration file that lists external repositories and hooks to run. It supports multiple languages, can automatically create isolated environments for hooks, and caches dependencies to speed up repeated runs. The typical workflow involves installing the framework, configuring a .pre-commit-config.yaml file, running pre-commit install to set up the Git hook, and then pre-commit run or committing to trigger the checks.

Common uses include enforcing style guides, trimming trailing whitespace, ensuring end-of-file conventions, and running linters or tests. While helpful for maintaining standards, pre-commit setups introduce additional processing before commits and require careful management of external hooks and dependencies.