Create pr-sha.yaml

.github/workflows/pr-sha.yaml

@@ -0,0 +1,40 @@
+name: PR sha
+
+on: 
+  pull_request:
+
+permissions: read-all
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Test
+        env:
+          CONTEXT: "${{ toJSON(github) }}"
+          # Exception for pull requests: https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows
+          PULL_REQUEST_SHA: "${{ github.event.pull_request.head.sha }}"
+        run: |
+          set -euo pipefail
+
+          git_sha="$(git log -1 --format='%H')"
+          github_sha="$GITHUB_SHA"
+          
+          echo "\"$git_sha\": $git_sha"
+          echo "\"$github_sha\": $github_sha"
+
+          if [[ "$GITHUB_EVENT_NAME" == "pull_request" ]]; then
+            github_sha="$PULL_REQUEST_SHA"
+            echo "pull request, updating github_sha"
+            echo "\"$github_sha\": $github_sha"
+          fi
+
+          if [[ "$git_sha" != "$github_sha" ]]; then
+              echo "mismatch git sha \"$git_sha\" != \"$github_sha\""
+              echo "GitHub context:"
+              echo "$CONTEXT"
+              echo
+              echo "Last 20 commits:"
+              git log -20
+              exit 1
+          fi