ci(native-pipeline): scope PRs from the base merge-base, not just HEAD~1

The scope job checked out with fetch-depth: 2 and passed github.event.before --
which is empty on pull_request events -- so the script fell back to
`git diff HEAD~1`, scoping a multi-commit PR off only its last commit (widgets
changed in earlier commits were silently dropped from build + test).

Check out full history (fetch-depth: 0) and pass the PR base SHA
(github.event.pull_request.base.sha); the script now diffs against the merge-base
with the base branch, covering every commit in the PR. Kept the per-widget
classifier and the dispatch path unchanged -- no new third-party action needed.

Author: vadim-v

.github/scripts/determine-widget-scope.sh

@@ -28,10 +28,19 @@ to_json_array() {
 }
 
 if [ "$event_name" == "pull_request" ]; then
+  # Diff against the MERGE-BASE with the PR base branch so every commit in the PR is
+  # considered, not just the latest. `before_commit` is the PR base SHA
+  # (github.event.pull_request.base.sha); the merge-base is where the PR branched off.
+  # Requires full history — the scope job checks out with fetch-depth: 0.
+  diff_base=""
   if git cat-file -e "$before_commit" 2>/dev/null; then
-    changed_files=$(git diff --name-only "$before_commit" "$current_commit")
+    diff_base=$(git merge-base "$before_commit" "$current_commit" 2>/dev/null || echo "$before_commit")
+  fi
+  if [ -n "$diff_base" ]; then
+    echo "Diffing against PR merge-base: $diff_base"
+    changed_files=$(git diff --name-only "$diff_base" "$current_commit")
   else
-    echo "Previous commit not found, using HEAD~1 as fallback"
+    echo "PR base commit unavailable, using HEAD~1 as fallback"
     changed_files=$(git diff --name-only HEAD~1 "$current_commit")
   fi
 

.github/workflows/NativePipeline.yml

@@ -120,12 +120,15 @@ jobs:
       - name: "Check out code"
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
-          fetch-depth: 2 # Fetch the latest two commits and its parent commit
+          # Full history so the scope script can diff against the PR base merge-base
+          # (covers every commit in the PR, not just the latest).
+          fetch-depth: 0
       - name: "Determine scope"
         id: scope
+        # Pass the PR base SHA (empty on non-PR events → the script's dispatch path handles it).
         run: |
           chmod +x ./.github/scripts/determine-widget-scope.sh
-          ./.github/scripts/determine-widget-scope.sh "${{ github.event_name }}" "${{ github.event.inputs.workspace }}" "${{ github.event.before }}" "${{ github.sha }}"
+          ./.github/scripts/determine-widget-scope.sh "${{ github.event_name }}" "${{ github.event.inputs.workspace }}" "${{ github.event.pull_request.base.sha || github.event.before }}" "${{ github.sha }}"
       - name: "Debug Scope Output"
         run: |
           echo "Scope is: ${{ steps.scope.outputs.scope }}"