.
├── packages/
│   ├── foo/
│   │   ├── src/
│   │   │   └── index.ts
│   │   ├── test/
│   │   │   └── index.ts
│   │   └── package.json
│   └── bar/
│       ├── src/
│       │   └── index.ts
│       ├── test/
│       │   └── index.ts
│       └── package.json
├── package.json
└── tasks.ts

$ yarn add --dev --ignore-workspace-root-check \
  @babel/core \
  @babel/register \
  @babel/preset-env \
  @babel/preset-typescript \
  @start/cli \
  @start/reporter-verbose \
  @start/plugin-sequence \
  @start/plugin-parallel \
  @start/plugin-xargs \
  @start/plugin-find \
  @start/plugin-find-git-staged \
  @start/plugin-remove \
  @start/plugin-read \
  @start/plugin-rename \
  @start/plugin-write \
  @start/plugin-lib-babel \
  @start/plugin-lib-typescript-generate \
  @start/plugin-lib-eslint \
  @start/plugin-lib-istanbul \
  @start/plugin-lib-tape \
  @start/plugin-lib-codecov

// package.json

{
  "private": true,
  "description": "Start example",
  "workspaces": [
    "packages/*"
  ],
  "devDependencies": {},
  "start": {
    // tasks file, default to `./tasks`
    "file": "./tasks"
    "require": [
      [
        "@babel/register",
        {
          "extensions": [
            ".ts",
            ".js"
          ]
        }
      ]
    ],
    "reporter": "@start/reporter-verbose"
  },
  "babel": {
    "presets": [
      [
        "@babel/preset-env",
        {
          "targets": {
            "node": "current"
          }
        }
      ],
      // Babel 7
      "@babel/preset-typescript"
    ]
  }
}

// tasks.ts

// write tasks file once, publish it and then reuse or even extend
// in all projects using `start.preset` option in `package.json`,
// something like `my-start-preset` package with everything included

import sequence from '@start/plugin-sequence'
import parallel from '@start/plugin-parallel'
import xargs from '@start/plugin-xargs'
import find from '@start/plugin-find'
import findGitStaged from '@start/plugin-find-git-staged'
import remove from '@start/plugin-remove'
import read from '@start/plugin-read'
import rename from '@start/plugin-rename'
import write from '@start/plugin-write'
import babel from '@start/plugin-lib-babel'
import typescriptGenerate from '@start/plugin-lib-typescript-generate'
import eslint from '@start/plugin-lib-eslint'
import {
  istanbulInstrument,
  istanbulReport,
  istanbulThresholds
} from '@start/plugin-lib-istanbul'
import tape from '@start/plugin-lib-tape'
import codecov from '@start/plugin-lib-codecov'

const babelConfig = {
  babelrc: false,
  presets: [
    [
      '@babel/preset-env',
      {
        targets: {
          node: 6
        },
        modules: false
      }
    ],
    '@babel/preset-typescript'
  ]
}

// each named export is a "task"
export const build = (packageName: string) =>
  sequence(
    find(`packages/${packageName}/src/**/*.ts`),
    read,
    babel(babelConfig),
    rename((file) => file.replace(/\.ts$/, '.js')),
    write(`packages/${packageName}/build/`)
  )

export const dts = (packageName: string) =>
  sequence(
    find(`packages/${packageName}/src/index.ts`),
    typescriptGenerate(`packages/${packageName}/build/`)
  )

export const pack = (packageName: string) =>
  sequence(
    find(`packages/${packageName}/build/`),
    remove,
    // child-processes
    parallel(['build', 'dts'])(packageName)
  )

// child processes
export const packs = xargs('pack')

export const dev = (packageName: string) =>
  watch(`packages/${packageName}/**/*.ts`)(
    build(packageName)
  )

export const lint = () =>
  sequence(
    findGitStaged(['packages/*/{src,test}/**/*.ts']),
    read,
    eslint()
  )

export const lintAll = () =>
  sequence(
    find(['packages/*/{src,test}/**/*.ts']),
    read,
    eslint()
  )

export const test = () =>
  sequence(
    find('coverage/'),
    remove,
    find('packages/*/src/**/*.ts'),
    istanbulInstrument({ esModules: true, extensions: ['.ts'] }),
    find('packages/*/test/**/*.ts'),
    tape(),
    istanbulReport(['lcovonly', 'html', 'text-summary']),
    istanbulThresholds({ functions: 100 })
  )

export const ci = () =>
  sequence(
    // nested task
    lintAll(),
    // nested task
    test(),
    find('coverage/lcov.info'),
    read,
    codecov
  )

$ yarn start
# or
$ npx start

One of the following task names is required:
* build
* dts
* pack
* packs
* dev
* lint
* lintAll
* test
* ci

$ yarn start build foo
$ yarn start dts foo
$ yarn start pack foo
$ yarn start packs foo bar
$ yarn start dev bar
$ yarn start lint
$ yarn start lintAll
$ yarn start test
$ yarn start ci