on-template.js

#!/usr/bin/env node

const { writeFileSync, readFileSync, unlinkSync } = require('fs')

const package = require('./package.json')
const packageLock = require('./package-lock.json')

const TEMPLATE_GITHUB_REPOSITORY = 'org/template'
const { GITHUB_REPOSITORY } = process.env

if (GITHUB_REPOSITORY === TEMPLATE_GITHUB_REPOSITORY) {
  // eslint-disable-next-line no-console
  console.info(`Not running inside ${TEMPLATE_GITHUB_REPOSITORY} repo.`)
  process.exit()
}

if (!GITHUB_REPOSITORY) {
  throw new Error('Unknown GITHUB_REPOSITORY.')
}

const TEMPLATE_PACKAGE_NAME = package.name
const PACKAGE_NAME = `@${GITHUB_REPOSITORY.toLowerCase()}`

/**
 * package.json
 */

package.name = PACKAGE_NAME
package.homepage = package.homepage.replace(TEMPLATE_GITHUB_REPOSITORY, GITHUB_REPOSITORY)
writeFileSync('./package.json', JSON.stringify(package, undefined, 2), { encoding: 'utf8' })

/**
 * package-lock.json
 */

packageLock.name = PACKAGE_NAME
writeFileSync('./package-lock.json', JSON.stringify(packageLock, undefined, 2), {
  encoding: 'utf8',
})

/**
 * README
 */

const readme = readFileSync('./README.md', { encoding: 'utf8' })
const newReadme = readme
  .split(TEMPLATE_PACKAGE_NAME)
  .join(PACKAGE_NAME)
  .split(TEMPLATE_GITHUB_REPOSITORY)
  .join(GITHUB_REPOSITORY)

writeFileSync('./README.md', newReadme, { encoding: 'utf8' })

/**
 * CLEAN UP
 */
unlinkSync('./on-template.js')
unlinkSync('./.github/workflows/on-template.yml')

on-template.yml

name: On Template

on:
  push:
    branches:
      - master

jobs:
  npm-publish:
    name: on template

    runs-on: ubuntu-latest

    steps:
      - name: Checkout
        uses: actions/checkout@v1

      - name: Setup Node
        uses: actions/setup-node@v1
        with:
          node-version: 12

      - name: Replace
        run: node ./on-template.js

      - name: push
        uses: github-actions-x/commit@v2.1
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          commit-message: 'chore: replaces template variables'
          rebase: 'true'

Make sure to replace TEMPLATE_GITHUB_REPOSITORY with your template repo name.