ci: add workflow to listen to comments for benchmark requests

.github/workflows/benchmark-comment-trigger.yml

@@ -0,0 +1,51 @@
+# This workflow is used to trigger benchmarks on a PR when a specific comment is added
+# to the PR.  The workflow runs on all PR comments containing the string 'benchmark'
+# and the string '@bench-bot'.  The workflow collects some information about the PR
+# and then forwards the information to the lance-bench workflow.
+#
+# The lance-bench repository is a public repository in the lancedb organization which
+# runs benchmarks against the Lance repository on a regular basis and stores the results
+# in a historical database.
+
+name: Benchmark Comment Trigger
+
+on:
+  issue_comment:
+    types: [created]
+
+jobs:
+  forward-to-bench:
+    # Only process comments on PRs that mention @bench-bot and contain 'benchmark'
+    if: |
+      github.event.issue.pull_request != null &&
+      contains(github.event.comment.body, '@bench-bot') &&
+      contains(github.event.comment.body, 'benchmark')
+    runs-on: ubuntu-latest
+    steps:
+      - name: Get PR details
+        id: pr
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const pr = await github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.issue.number
+            });
+
+            core.setOutput('head_sha', pr.data.head.sha);
+
+      - name: Forward to lance-bench
+        uses: peter-evans/repository-dispatch@v2
+        with:
+          token: ${{ secrets.LANCE_BENCH_DISPATCH_TOKEN }}
+          repository: lancedb/lance-bench
+          event-type: pr-comment
+          client-payload: |
+            {
+              "comment_body": ${{ toJson(github.event.comment.body) }},
+              "comment_user": "${{ github.event.comment.user.login }}",
+              "pr_number": ${{ github.event.issue.number }},
+              "pr_head_sha": "${{ steps.pr.outputs.head_sha }}",
+              "repository": "${{ github.repository }}"
+            }