---
title: "Git Tips - Global Pre-commit Hooks"
date: 2020-01-01T21:00:39Z
tags: [git, testing, bash]
---

[Git hooks][1] are a feature of the Git VCS that allow you to fire off custom logic on the client side when you take
actions in your repository. These are shell scripts in the `.git/hooks/` directory of your repository, but they can also
 exist in your home directory at `~/.githooks/`.

Any hooks found in `~/.githooks/` are executed globally, this makes it easy to setup a custom workflow that is consistent 
across your entire machine.

## Automatically lint and test on commit

One of my favorite hooks is the `~/.githooks/pre-commit` hook that auto runs test and lint commands from a `makefile` or 
`package.json` if they're found:

```sh
{{<highlight bash "linenos=table">}}
#!/usr/bin/env bash

if [ -f "$PWD/makefile" ] && [ ! -z "$(cat $PWD/makefile | grep '^lint:')" ]; then
    echo "running make lint"
    make lint
elif [ -f "$PWD/package.json" ] && [ ! -z "$(cat $PWD/package.json | grep "^\"lint\":")" ]; then
    echo "running npm run lint"
    npm run lint
fi

if [ -f "$PWD/makefile" ] && [ ! -z "$(cat $PWD/makefile | grep '^test:')" ]; then
    echo "running make test"
    make test
elif [ -f "$PWD/package.json" ] && [ ! -z "$(cat $PWD/package.json | grep "^\"test\":")" ]; then
    echo "running npm run test"
    npm run test
fi
{{</highlight>}}
```

The `/usr/bin/env bash` piece ensures that the script has access to all of the environment variables you expect in your 
regular shell.

If the test or lint command fails then the `git commit` command fails. If I absolutely need to commit something in spite
of the lint/test results I can do `git commit --no-verify` to skip the `pre-commit` hook.

[1]: https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks "Git hooks"