title: Using an array of values to repeat a step in GitHub Actions workflow
body: <p>I am trying to create a GitHub Actions workflow which would collect specific paths changed in last commit and run a step for each of collected paths, if any.</p>
  
  <p>Currently, in my workflow I'm creating an array of paths, but I'm not sure how to proceed with my array:</p>
  
  <pre><code>name: Test
  
  on:
    push
  
  jobs:
    test:
      runs-on: ubuntu-latest
      steps:
        - uses: actions/checkout@v1
  
        # This step will create "an array" of strings, e.g. "path1 path2 path3"
        - name: array
          id: arr
          run: |
            arr=()
            for i in "$(git diff-tree --no-commit-id --name-only -r ${{ github.sha }})"
            do
              if [[ $i == *"path1"* ]]; then
                arr+=("path1")
              fi
              if [[ $i == *"path2"* ]]; then
                arr+=("path2")
              fi
            done
            echo ::set-output name=arr::${arr[@]}
  
        # How to run this step by iterating the `${{ steps.arr.outputs.arr }}`?
        - name: reviewdog-lint
          uses: reviewdog/action-eslint@v1
          with:
            github_token: ${{ secrets.GITHUB_TOKEN }}
            reporter: github-pr-review
            eslint_flags: 'my_project/some_folder/${{ SINGLE_PATH }}/'  # `SINGLE_PATH` would be a path from the array
  </code></pre>
  
  <p>Is something like this even possible in the first place? If not, what would be recommended way to loop through some values and use them as arguments in other workflow steps?</p>