How to add gitignored files to Heroku (and how not to)

Sometimes, you want to add extra files to Heroku or Git, such as built files, or secrets; but it is already in .gitignore, so you have to build on the server.

You have options, as this command is available.

git push heroku new-branch:master

But how do I create such new-branch.

A naive solution would be to use git switch, but this endangers gitignored files as well. (It might disappear when you switch branch.)

That's where git worktree comes in.

I can use a real shell script, but I feel like using Node.js is much easier (and safer due to pour-console).

So, it is basically like this.

async function deploy (
  callback,
  deployFolder = 'dist',
  deployBranch = 'heroku',
  deployMessage = 'Deploy to Heroku'
) {
  // Ensure that dist folder isn't exist in the first place
  await pour('rm -rf dist')

  try {
    await pour(`git branch ${deployBranch} master`)
  } catch (e) {
    console.error(e)
  }

  await pour(`git worktree add -f ${deployFolder} ${deployBranch}`)

  await callback(deployFolder, deployBranch)

  await pour('git add .', {
    cwd: deployFolder
  })

  await pour([
    'git',
    'commit',
    '-m',
    deployMessage
  ], {
    cwd: deployFolder
  })

  await pour(`git push -f heroku ${deployBranch}:master`, {
    cwd: deployFolder
  })

  await pour(`git worktree remove ${deployFolder}`)

  await pour(`git branch -D ${deployBranch}`)
}

deploy(async (deployFolder) => {
  fs.writeFileSync(
    `${deployFolder}/.gitignore`,
    fs.readFileSync('.gitignore', 'utf8').replace(ADDED_FILE, '')
  )
  fs.copyFileSync(
    ADDED_FILE,
    `${deployFolder}/${ADDED_FILE}`
  )
}).catch(console.error)

How not to commit

Apparently, this problem is easily solved on Heroku with

pour(`heroku config:set SECRET_FILE=${fs.readFileSync(secretFile, 'utf8')}`)

Just make sure the file is deserializable.

You might even write a custom serializing function, with

JSON.stringify(obj[, replacer])

JSON.parse(str[, reviver])

Don't forget that JSON object is customizable.