Run pre-commit in forks (#556)

Author: jirikuncar

.github/workflows/test.yml

@@ -21,17 +21,26 @@ jobs:
       !contains(github.event.pull_request.labels.*.name, 'ci/skip') &&
       !contains(github.event.pull_request.head.ref, 'datadog-api-spec/test/')
     steps:
+      # Run only in this repository
       - name: Get GitHub App token
         id: get_token
+        if: github.event.pull_request.head.repo.full_name == github.repository
         uses: tibdex/github-app-token@v1
         with:
           app_id: ${{ secrets.PIPELINE_GITHUB_APP_ID }}
           private_key: ${{ secrets.PIPELINE_GITHUB_APP_PRIVATE_KEY }}
       - uses: actions/checkout@v2
+        if: github.event.pull_request.head.repo.full_name == github.repository
         with:
           fetch-depth: 0
           ref: ${{ github.event.pull_request.head.sha }}
           token: ${{ steps.get_token.outputs.token }}
+      # Fetch a fork of the repo
+      - uses: actions/checkout@v2
+        if: github.event.pull_request.head.repo.full_name != github.repository
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha }}
       - name: Install pre-commit
         run: python -m pip install pre-commit
       - name: set PY
@@ -46,7 +55,7 @@ jobs:
         run: |
           pre-commit run --from-ref ${{ github.event.pull_request.base.sha }} --to-ref ${{ github.event.pull_request.head.sha }} --show-diff-on-failure --color=always
       - name: Commit changes
-        if: ${{ failure() }}
+        if: github.event.pull_request.head.repo.full_name == github.repository && failure()
         run: |-
           git add -A
           git config user.name "${GIT_AUTHOR_NAME}"