Add a workflow that attaches to Bencher bare metal jobs

.github/workflows/bare_metal_attach.yml

@@ -0,0 +1,52 @@
+on:
+  repository_dispatch:
+    types: [bencher_run]
+
+jobs:
+  attach_pr_benchmarks:
+    name: Post PR Benchmark Results from Bencher Bare Metal
+    permissions:
+      checks: write
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+      - name: Show the type of each dispatch payload field, never its value
+        run: jq '.client_payload // {} | map_values(if type == "object" then map_values(type) else type end)' "$GITHUB_EVENT_PATH"
+      - name: Resolve the Bencher CLI commit
+        id: bencher-cli
+        run: |
+          sha="$(git ls-remote https://github.com/bencherdev/bencher refs/heads/u/ep/callback/smoke | cut -f1)"
+          test -n "$sha"
+          echo "sha=$sha" >> "$GITHUB_OUTPUT"
+          echo "key=bencher-cli-$ImageOS-$RUNNER_ARCH-$sha" >> "$GITHUB_OUTPUT"
+      - name: Restore the Bencher CLI
+        id: restore-bencher-cli
+        uses: actions/cache/restore@v5
+        with:
+          path: ~/.bencher-cli
+          key: ${{ steps.bencher-cli.outputs.key }}
+      - name: Install the Bencher CLI
+        if: steps.restore-bencher-cli.outputs.cache-hit != 'true'
+        env:
+          BENCHER_SHA: ${{ steps.bencher-cli.outputs.sha }}
+        run: cargo install --git https://github.com/bencherdev/bencher --rev "$BENCHER_SHA" --locked --root ~/.bencher-cli bencher_cli
+      - name: Save the Bencher CLI
+        if: steps.restore-bencher-cli.outputs.cache-hit != 'true'
+        uses: actions/cache/save@v5
+        with:
+          path: ~/.bencher-cli
+          key: ${{ steps.bencher-cli.outputs.key }}
+      - name: Add the Bencher CLI to the path
+        run: echo "$HOME/.bencher-cli/bin" >> "$GITHUB_PATH"
+      - name: Post PR Benchmark Results with Bencher
+        env:
+          JOB_UUID: ${{ github.event.client_payload.bencher.job }}
+          PROJECT_SLUG: ${{ github.event.client_payload.bencher.project }}
+        run: |
+          bencher run \
+          --host https://dev.api.bencher.dev \
+          --project "$PROJECT_SLUG" \
+          --token '${{ secrets.DEV_BENCHER_API_TOKEN }}' \
+          --job "$JOB_UUID" \
+          --error-on-alert \
+          --github-actions '${{ secrets.GITHUB_TOKEN }}'