Fix update-docs for external contributions

.github/workflows/update-docs.yml

@@ -18,15 +18,25 @@ jobs:
         name: Checkout PR
         uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # ratchet:actions/checkout@v3
         with:
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
           ref: ${{ github.event.pull_request.head.ref }}
 
       - if: github.event_name == 'push'
         name: Checkout branch
         uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # ratchet:actions/checkout@v3
 
       - name: Generate TF docs
+        if: github.event.pull_request.head.repo.full_name == github.repository
         uses: terraform-docs/gh-actions@f6d59f89a280fa0a3febf55ef68f146784b20ba0 # ratchet:terraform-docs/gh-actions@v1.0.0
         with:
           find-dir: .
           git-commit-message: "docs: auto update terraform docs"
           git-push: true
+
+      - name: Check TF docs
+        if: github.event.pull_request.head.repo.full_name != github.repository
+        uses: terraform-docs/gh-actions@f6d59f89a280fa0a3febf55ef68f146784b20ba0 # ratchet:terraform-docs/gh-actions@v1.0.0
+        with:
+          find-dir: .
+          fail-on-diff: true
+          git-push: false