Automatic GitHub deployments

auto-deploy.js

//
// README:
// - Listens for PUSH events
// - Fetches the ref pushed via the given remote
// - Sets the repositories HEAD to latest ref
// - Checks out the new HEAD (--force)
// - Install dependencies from package.json
// - Calls `npm run reload` (My app uses this)
// - Calls `nginx -s reload` (My app also uses this)
//
// Usage:
//     export SECRET=YOUR_GITHUB_WEBHOOK_SECRET
//     export CWD=/path/to/your/project
//     export REMOTE=origin
//     export SOCKET_PRIV="your_user:your_group"
//     export GIT_AUTHOR="Your Name"
//     export GIT_EMAIL="Your Email"
//
// As root:
//     node auto-deploy
//

['SECRET', 'CWD', 'REMOTE', 'SOCKET_PRIV', 'GIT_AUTHOR', 'GIT_EMAIL']
  .forEach(function(ENV) {
    if (!(ENV in process.env)) {
      console.error('Missing environment variable: ' + ENV);
      process.exit();
    }
  });

var express = require('express');
var Git = require('nodegit');
var exec = require('child_process').execSync;
var createHandler = require('github-webhook-handler');

var GHWebHook = createHandler({ path: '/', secret: process.env.SECRET });
var me = Git.Signature.now(process.env.GIT_AUTHOR, process.env.GIT_EMAIL);

GHWebHook.on('push', function (event) {
  var payload = event.payload;

  if (payload.ref !== 'refs/heads/master') {
    return;
  }

  function fetchRemote(repo) {
    console.log('Fetching remote', process.env.REMOTE);

    return repo.getRemote(process.env.REMOTE).then(function(remote) {
      remote.setCallbacks({
        credentials: function(url, userName) {
          return Git.Cred.sshKeyFromAgent(userName);
        }
      });

      return remote.fetch([payload.ref], me, 'Fetched latest deployment');
    }).then(function() {
      return repo; 
    });
  }

  function resetAndCheckout(repo) {
    return repo.getReference(process.env.REMOTE).then(function(ref) {
      console.log('Changing HEAD to', ref.target());

      return repo.setHead(ref.name(), me, 'Set head to ' + ref.target());
    }).then(function() {
      console.log('Checking out HEAD');

      return Git.Checkout.head(repo, {
        checkoutStrategy: Git.Checkout.STRATEGY.FORCE
      });
    });
  }

  function reloadAndComplete() {
    console.log('Ensure Node modules are up-to-date');
    exec('npm install', { cwd: process.env.CWD });

    console.log('Reloading application');
    exec('npm run reload', { cwd: process.env.CWD });

    console.log('Resetting NGINX');
    exec('nginx -s reload');

    console.log('Completed deployment');
  }

  // Async-flow.
  Promise.resolve(process.env.CWD)
    .then(function(path) {
      console.log('Opened repository');
      return Git.Repository.open(path); 
    })
    .then(fetchRemote)
    .then(resetAndCheckout)
    .then(reloadAndComplete)
    .catch(function(ex) {
      console.log(ex.stack);
    });
});

// Attempt to clean up previous socket and re-bind.
try { exec('rm ./socket'); } catch (ex) {}
express().use(GHWebHook).listen('./socket');
exec('chown ' + process.env.SOCKET_PRIV + ' ./socket');

@tbranyen Thanks for sharing this. A late question: I was wondering if there is any reason behind using execSync and not making asynchronous calls instead on line 76-87?