Commit-msg git hook with node.js

commit-msg

#!/usr/bin/env node

/**
 * 
 * This code will ensure that before every commit in your client repository, your branch name and commit message adheres to a certain contract.
 * In this example, branch names must be like 'feature/AP-22-some-feature-name' or 'hotfix/AP-30-invitation-email-not-sending', and commit messages must start like some issue code, like AP-100 or AP-101.
 * 
 * 'AP' just stands for Acme Platform and is an example. I made this example with Jira in mind, since Jira issue codes have this structure -as far as I know-, but is pretty easy to change it to any other issue id like #100 or $-AP-120, or whatever.
 * 
 * In order for this to work, you should go to .git/hooks in any git client repository and create a commit-msg file (or modify the provided by default, commit-msg.sample) with
 * this contents.
 * 
 * You need an await/async compliant version of node installed in your machine.
 * 
 * Don't forget to make your file executable!
 */

const fs = require('fs');
const childProcessExec = require('child_process').exec;
const util = require('util');
const BRANCH_CONTRACT = /^(feature|hotfix)\/AP-[0-9]{1,6}-/;
const CODE_CONTRACT = /AP-[0-9]{1,6}-/;
const TIMEOUT_THRESHOLD = 3000;

const exec = util.promisify(childProcessExec);

checkCommitMessage();
hookCleanup();

async function checkCommitMessage(){

  const message = fs.readFileSync(process.argv[2], 'utf8').trim();
  let branchName = '';
  try{
    branchName = await getCurrentBranch();
  }
  catch (e){
    handleGitBranchCommandError(e);
  }

  if( ! BRANCH_CONTRACT.test(branchName) ){
    handleBadBranchName();
  }

  if(! CODE_CONTRACT.test(message) ){
    handleBadCommitMessage();
  }
  process.exit(0);
}

async function getCurrentBranch() {

  const branchesOutput = await exec('git branch');
  if( branchesOutput.stderr){
    throw new Error(stderr);
  }
  const branches = branchesOutput.stdout;
  return branches.split('\n').find(b => b.trim().charAt(0) === '*' ).trim().substring(2);
}

function handleGitBranchCommandError(e){
  console.log('something bad happened when trying to read the repository branches using the "git branch" command');
  console.log('this is script is intended to be run as a git hook inside a git repository. Are you sure you\'re calling it properly?');
  console.log('the error provided by the "git branch" invocation was the following:');
  console.log(e.getMessage() );
  console.log('----');
  console.log('Your commit will be rejected. This script will terminate.');
  process.exit(1);
}

function handleBadBranchName(){
  
  console.log('There is something wrong with your branch name');
  console.log('branch names in this project must adhere to this contract:' + BRANCH_CONTRACT);
  console.log('they must start either with the "feature" or "hotfix" word, followed by a "/" char and then a Jira valid issue identifier, followed by a dash');
  console.log('Your commit will be rejected. You should rename your branch to a valid name, for instance, you could run a command like the following to rename your branch:');
  console.log('git branch -m feature/HP-1201-some-killer-feature');
  console.log('if you thing there is something wrong with this message, or that your branch name is not being validated properly, check the commit-msg git hook');
  process.exit(1);
}

function handleBadCommitMessage(){
  
  console.log('There is something wrong with your commit message');
  console.log('it should start with a valid Jira issue code, followed by a dash, thus adhering to this contract:' + CODE_CONTRACT);
  console.log('your commit will be rejected. Please re-commit your work again with a proper commit message.');
  console.log('if you thing there is something wrong with this message, or that your commit message is not being validated properly, check the commit-msg git hook');
  process.exit(1);
}

function hookCleanup(){

  setTimeout(() => {
    console.log('This is a timeout message from your commit-msg git hook. If you see this, something bad happened in your pre-commit hook, and it absolutely did not work as expected.');
    console.log(' Your commit will be rejected. Please read any previous error message related to your commit message, and/or check the commit-msg git hook script.');
    console.log(' You can find more info in this link: https://git-scm.com/book/uz/v2/Customizing-Git-An-Example-Git-Enforced-Policy');
    process.exit(1);
  },TIMEOUT_THRESHOLD);

}