Trigger docs-draft-writer pipeline on merge to main

.buildkite/pipeline.yml

@@ -413,6 +413,11 @@ steps:
           artifacts: "releases/*.tar.gz;releases/*.zip"
           attestation_name: "buildkite-agent-github-releases.attestation.json"
 
+  - name: ":memo: Trigger docs draft"
+    if: build.branch == "main"
+    soft_fail: true
+    command: .buildkite/steps/trigger-docs-draft.sh
+
   - name: ":pipeline: Upload Release Pipeline"
     key: upload-release-steps
     depends_on:

.buildkite/steps/trigger-docs-draft.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+# Extract the PR number from the commit message.
+# Handles both formats:
+#   Squash merge: "Some title (#1234)"
+#   Merge commit: "Merge pull request #1234 from ..."
+PR_NUMBER="$(echo "${BUILDKITE_MESSAGE}" | grep -oP '#\K[0-9]+' | head -1 || true)"
+
+if [ -z "${PR_NUMBER}" ]; then
+  echo "Could not extract PR number from commit message, skipping"
+  exit 0
+fi
+
+echo "--- :memo: Triggering docs-draft-writer for buildkite/agent#${PR_NUMBER}"
+
+buildkite-agent pipeline upload <<EOF
+steps:
+  - trigger: "docs-draft-writer"
+    label: ":memo: Docs draft for buildkite/agent#${PR_NUMBER}"
+    async: true
+    soft_fail: true
+    build:
+      message: "Docs draft for buildkite/agent#${PR_NUMBER}"
+      branch: "main"
+      env:
+        UPSTREAM_REPO: "buildkite/agent"
+        UPSTREAM_PR_NUMBER: "${PR_NUMBER}"
+EOF