title: Lerna always lists all packages ready to publish when running workflow of Github actions
body: <p>Lerna does not correctly detect packages change during running workflow of Github actions.</p>
  
  <ol>
  <li><p>If I make none packages related changes, commit and run<code>lerna updated</code>locally. it tells me <strong>No changed packages found</strong> which is correct and expected.</p></li>
  <li><p>If I make package related changes, commit and run <code>lerna updated</code> locally. it tells me found <strong>x packages ready to publish</strong> which is also correct and expected.</p></li>
  </ol>
  
  <p><strong>However, if I push the commit based on <code>1 or 2</code>. the step which I run <code>lerna updated</code> in my github actions workflow always tells/lists me all the package are available to publish which is wrong.</strong></p>
  
  <p><strong>I am wondering why and how to fix it ???</strong></p>
  
  <p><strong>here is what I see locally if I made none packages related changes</strong></p>
  
  <pre><code>lerna notice cli v3.20.2
  lerna info versioning independent
  lerna info Looking for changed packages since @xxx/bar@2.3.4
  lerna info No changed packages found
  </code></pre>
  
  <p><strong>here is what I see on workflow log after pusing the none packages related changes to Github</strong></p>
  
  <pre><code>&gt; lerna updated -l
  
  lerna notice cli v3.20.2
  lerna info versioning independent
  lerna info Assuming all packages changed
  @xxx/bar  v2.3.4 packages/Bar
  @xxx/foo  v1.4.4 packages/Foo
  @xxx/hulk v1.0.4 packages/Hulk
  lerna success found 3 packages ready to publish
  </code></pre>
  
  <p><strong>here is my workflows</strong></p>
  
  <pre><code>name: Publish
  on:
    push:
      branches:
        - master
  jobs:
    unit-test:
      name: UnitTest
      runs-on: ubuntu-latest
      steps:
        - uses: actions/checkout@v2
        - uses: actions/setup-node@v1
          with:
            node-version: 12
        - run: npm ci
        - run: npm test
  
    publish:
      name: Publish NPM Packages
      needs: unit-test
      runs-on: ubuntu-latest
      steps:
        - uses: actions/checkout@v2
        - uses: actions/setup-node@v1
          with:
            node-version: 12
            registry-url: https://registry.npmjs.org/
        - run: npm ci
        - run: git config --global user.email "xxx"
        - run: git config --global user.name "xxx"
        - run: npm run updated
          env:
            NODE_AUTH_TOKEN: ${{secrets.NPM_AUTH_TOKEN}}
  </code></pre>
  
  <p><strong>here is my package.json</strong></p>
  
  <pre><code>{
    "name": "root",
    "devDependencies": {
      "jest": "^25.1.0",
      "lerna": "^3.20.2"
    },
    "scripts": {
      "updated": "lerna updated -l",
      "test": "jest"
    }
  }
  
  </code></pre>
  
  <p><strong>here is my lerna setting</strong></p>
  
  <pre><code>{
    "packages": [
      "packages/*"
    ],
    "version": "independent",
    "command": {
      "publish": {
        "allowBranch": "master",
        "conventionalCommits": true,
        "message": "chore(release): updated release notes and package versions"
      }
    }
  }
  </code></pre>