commit-msg Git hook to ask user for an issue ID when he commits and prepend it to the original commit message

commit-msg.issue-id-prompt.js

#!/usr/bin/env node
var fs = require('fs'),
    util = require('util');

// Rattern to format the message with the issue ID
var MESSAGE_FORMAT = '[%s] %s';

// Git commit messages are stored in a file, passed as argument to the script
// First and second arguments will be 'node' and the name of the script
var commitFile = process.argv[2];

// Let's start by reading the current commit message
fs.readFile(commitFile, 'utf-8', function (err, message) {

  if(err) {
    console.log('Original commit message could not be read :(');
    process.exit(-1);
  }

  if (message === '') {

    // If the commit message is empty, just pass it on to git
    // The commit wil abort anyway
    process.exit(0);
  }

  // Now we have the message, let's read the user input
  var stream = fs.createReadStream('/dev/tty');
  stream.setEncoding('utf-8');

  // Displays a message to the user when the hook's ready to get input
  stream.on('open', function () {

    console.log('Which issue were you working on?');
  });

  // Handles the data provided by the user
  stream.on('data',  function (data) {

    // First, we get rid of the trailing carriage return at the end
    data = data.replace('\n','');
    // User must provide an issue ID, so we'll prompt them again if they don't
    if (data === '') {

      console.log('You need to provide an issue ID. What issue were you working on?');
      return;
    }

    // Otherwise we prepend the issue ID to the commit message
    var finalMessage = util.format(MESSAGE_FORMAT, data, message);

    // And replace the content of the commit message file
    fs.writeFile(commitFile, finalMessage, function(err) {

      if (err) {
        console.log('Commit message could not be written :(');
        console.log(err);
        process.exit(-2);
      }

      console.log('The issue ID has been added to the commit message.\nPress RETURN to complete commit');
      process.exit();
    });
  });
});

Awesome 👍