build-id.js

const fs = require('fs')
const path = require('path')
const { execFile } = require('child_process')

function lastCommitId(dir) {
  return new Promise((resolve, reject) => {
    const gitArgs = [
      `--git-dir=${path.join(dir, '.git')}`,
      `--work-tree=${dir}`,
      'rev-parse',
      'HEAD',
    ]

    execFile('git', gitArgs, (err, stdout, stderr) => {
      if (err) return reject(err)
      if (stderr) return reject(String(stderr).trim())
      if (stdout) return resolve(String(stdout).trim())

      return reject(new Error(`No output from command: git ${gitArgs.join(' ')}`))
    })
  })
}

function findDotGit(inputDir, maxAttempts = 999) {
  // inputDir may not be the project root so look for .git dir in parent dirs too
  let dir = inputDir

  const { root } = path.parse(dir)
  let attempts = 0 // protect against infinite tight loop if libs misbehave
  while (dir !== root && attempts < maxAttempts) {
    attempts += 1
    try {
      fs.accessSync(path.join(dir, '.git'), (fs.constants || fs).R_OK)
      break
    } catch (_) {
      dir = path.dirname(dir)
    }
  }
  if (dir === root || attempts >= maxAttempts) {
    dir = inputDir
  }

  return dir
}

function determineBuildId({ dir } = { dir: __dirname }) {
  return lastCommitId(findDotGit(dir))
}

module.exports = {
  determineBuildId,
  findDotGit,
  lastCommitId,
}