Generate short hash for e2e trigger directly with git (#123)

<!-- The PR description should answer 2 (maybe 3) important questions:
-->

### What

The generated hashes from `short-sha` did not always match the Docker
image. This is because Github Actions creates a new merge commit for
pull requests: https://github.com/orgs/community/discussions/26325

### How

Find the actual source commit and create a hash from that.

.github/workflows/e2e-test.yaml

@@ -11,11 +11,17 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      - uses: actions/checkout@v4
+
+      # pull requests create a new merge commit so we have to work our way back
+      # to the actual commit so it matches the Docker image
       - name: Generate short SHA
-        uses: benjlevesque/[email protected]
-        id: short-sha
-        with:
-          length: 9
+        run: |
+          if [ "$GITHUB_EVENT_NAME" == "pull_request" ]; then
+            GITHUB_SHA=$(cat $GITHUB_EVENT_PATH | jq -r .pull_request.head.sha)
+          fi
+          echo "hash=$(git rev-parse --short=9 "$GITHUB_SHA")" >> $GITHUB_OUTPUT
+        id: short-git-hash
 
       - name: Wait for Docker image to be created
         uses: lewagon/[email protected]
@@ -28,7 +34,7 @@ jobs:
         uses: aurelien-baudet/workflow-dispatch@v2
         id: workflow_dispatch
         with:
-          inputs: '{ "connector": "${{ steps.short-sha.outputs.sha }}" }'
+          inputs: '{ "connector": "${{ steps.short-git-hash.outputs.hash }}" }'
           repo: hasura/v3-e2e-testing
           ref: main
           token: ${{ secrets.E2E_WORKFLOW_PAT }}