Run benchmarks in CI

.github/workflows/benchmark.yml

@@ -0,0 +1,74 @@
+name: Benchmark
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+permissions:
+  contents: read
+
+# Ensure scripts are run with pipefail. See:
+# https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#exit-codes-and-error-action-preference
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  benchmark:
+    runs-on: ubuntu-latest
+    # runs-on:
+    # - 'self-hosted'
+    # - '1ES.Pool=TypeScript-1ES-GitHub-Large'
+    # - '1ES.ImageOverride=mariner-2.0'
+
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          submodules: true
+          filter: blob:none # https://github.blog/2020-12-21-get-up-to-speed-with-partial-clone-and-shallow-clone/
+          fetch-depth: 0 # Default is 1; need to set to 0 to get the benefits of blob:none.
+      - uses: actions/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af # v4.1.0
+      - uses: actions/setup-go@41dfa10bad2bb2ae585af6ee5bb4d7d973ad74ed # v5.1.0
+        with:
+          go-version: '>=1.23.0'
+
+      - run: npm ci
+
+      - name: Run benchmark
+        run: go test -run='^$' -bench=. -benchmem -count=10 ./... | tee new.txt
+
+      - name: Switch to parent commit
+        run: git switch --detach HEAD^1
+
+      - run: npm ci
+
+      - run: git submodule update --init --recursive
+
+      - name: Run benchmark
+        run: go test -run='^$' -bench=. -benchmem -count=10 ./... | tee old.txt
+
+      - run: go install golang.org/x/perf/cmd/benchstat@latest
+
+      - name: Compare benchmarks
+        run: benchstat old.txt new.txt | tee benchstat.txt
+
+      - uses: actions/upload-artifact@b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882 # v4.4.3
+        with:
+          name: benchmarks
+          path: |
+            old.txt
+            new.txt
+            benchstat.txt
+
+      - name: Create step summary
+        run: |
+          echo "See $GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID for more info."
+          echo "# Benchmark Results" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo '```' >> $GITHUB_STEP_SUMMARY
+          cat benchstat.txt >> $GITHUB_STEP_SUMMARY
+          echo '```' >> $GITHUB_STEP_SUMMARY