replace checkout code in CI

.github/workflows/Test-CI-main.yml

@@ -1,13 +1,10 @@
 name: "Test Library CI (main)"
 
-# This workflow always run in the context of Classiq/classiq-library (base repo) but might use a branch from a fork to test its contribution
-# PRs from users (should be from a fork) need to targePrint repository namet `main` branch which runs against `prod` environment
-
 on:
-  push: # Trigger the workflow on push to the specific branch
+  push:
     branches:
       - main
-  pull_request_target: # Trigger the workflow on pull requests targeting the specific branch
+  pull_request_target:
     # Note: `pull_request_target` ensures that the tests run in the context of the `main` branch, not in the user's fork.
     branches:
       - main
@@ -26,62 +23,33 @@
 
     runs-on: ubuntu-latest
 
+    env:
+      # Previosly we had:
+      #   if workflow_dispatch: True
+      #   if pull_request_target: False
+      #   if push: nothing, which translates to False
+      SHOULD_TEST_ALL_FILES: ${{ github.event_name == 'workflow_dispatch' }}
+
     steps:
       #
       # Setup Repository
       #
-      - name: Checkout repository
+      - name: Checkout (push / workflow_dispatch)
+        if: github.event_name != 'pull_request_target'
         uses: actions/checkout@v4
 
-      - name: Checkout the target branch
-        id: checkout
-        run: |
-          set -ex
-
-          # Debugging: initial git status
-          echo "==== Git status before checkout ===="
-          git status
-
-          # Handle different GitHub Actions events
-          if [[ "${{ github.event_name }}" == "pull_request_target" ]]; then
-            echo "Handling pull_request_target event"
-            echo "SHOULD_TEST_ALL_FILES=false" >> $GITHUB_ENV
-
-            if [ "$REPO_NAME" != "${{ github.repository }}" ]; then
-              echo "PR from a fork detected. Checking out the fork's branch."
-              git remote add fork "https://github.com/$REPO_NAME.git"
-              git fetch fork "$BRANCH_NAME"
-              git checkout -B ci-testing-branch FETCH_HEAD # Tested code is comming from this branch (contributer's)
-            else
-              echo "PR from the same repository detected. Checking out the branch."
-              git fetch origin "$BRANCH_NAME"
-              git checkout "$BRANCH_NAME"
-            fi
-
-          elif [[ "${{ github.event_name }}" == "workflow_dispatch" ]]; then
-            echo "Handling workflow_dispatch event: No checkout needed"
-            echo "SHOULD_TEST_ALL_FILES=true" >> $GITHUB_ENV
-            echo "list_of_ipynb_changed=**/*.ipynb" >> $GITHUB_ENV
-
-          elif [[ "${{ github.event_name }}" == "push" ]]; then
-            echo "Handling push event: No checkout needed"
-
-          else
-            echo "Unsupported event type: ${github.event_name}. Exiting."
-            exit 1
-          fi
-
-          # Debugging: final git status
-          echo "==== Git status after checkout ===="
-          git status
-        env:
-          REPO_NAME: "${{ github.event.pull_request.head.repo.full_name }}"
-          BRANCH_NAME: "${{ github.event.pull_request.head.ref }}"
+      - name: Checkout PR head (pull_request_target)
+        if: github.event_name == 'pull_request_target'
+        uses: actions/checkout@v4
+        with:
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          ref: ${{ github.event.pull_request.head.sha }}
+          persist-credentials: false
 
       #
       # Setup Python
       #
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
           python-version: "3.11"