action.yml

# Sparse checkout: https://github.com/actions/checkout/issues/172
# actions/checkout@v2 does not support sparse checkout as of Oct 2021

name: Sparse checkout
inputs:
  token:
    description: 'GitHub token'
    default: ${{ github.token }}

  paths:
    description: 'Paths to add to the sparse checkout'
    required: true
    type: string # There is no type "list" in Github Actions as of Oct 2021

runs:
  using: composite
  steps:
    - name: Perform sparse checkout
      shell: bash
      run: |
        REPO="https://${GITHUB_ACTOR}:${{ inputs.token }}@github.com/${GITHUB_REPOSITORY}.git"
        # For a partial checkout we need a branch name (like issue/APP-XXXX)
        # Now, follow the hands:
        #   GITHUB_HEAD_REF is defined only for pull_request triggers and it's a branch name
        #   GITHUB_REF is defined only for branch push triggers and it's a ref (ref/heads/issue/APP-XXXX)
        PR_BRANCH=${GITHUB_HEAD_REF}
        PUSH_BRANCH=${GITHUB_REF#refs/heads/}
        BRANCH="${PR_BRANCH:-${PUSH_BRANCH}}" # Pick one of the two

        git clone --filter=blob:none --no-checkout --depth 1 --single-branch -b "$BRANCH" --sparse "$REPO" .
        git sparse-checkout init --cone
        git sparse-checkout add ${{ inputs.paths }}
        git checkout