Allow pull requests, and report correct commit oid and ref

README.md

@@ -18,6 +18,7 @@ name: "Code Scanning - Action"
 
 on:
   push:
+  pull_request:
   schedule:
     - cron: '0 0 * * 0'
 
@@ -33,6 +34,17 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v2
+        with:
+          # Must fetch at least the immediate parents so that if this is
+          # a pull request then we can checkout the head of the pull request.
+          # Only include this option if you are running this workflow on pull requests.
+          fetch-depth: 2
+
+      # If this run was triggered by a pull request event then checkout
+      # the head of the pull request instead of the merge commit.
+      # Only include this step if you are running this workflow on pull requests.
+      - run: git checkout HEAD^2
+        if: ${{ github.event_name == 'pull_request' }}
 
       # Initializes the CodeQL tools for scanning.
       - name: Initialize CodeQL