internal: [TE-5828] Add bktec plan step to collect commit metadata on agent builds

.buildkite/pipeline.yml

@@ -37,6 +37,34 @@ steps:
         mount-buildkite-agent: true
         run: lint
 
+  # Send git commit metadata to the Test Engine plan-metadata pipeline on
+  # every build. Plan output is discarded -- the Tests and Coverage group
+  # below continues to use its declared parallelism. This step has no
+  # depends_on and no dependents, and is soft_fail, so a Test Engine API
+  # hiccup never blocks the build.
+  #
+  # Runs inside the `agent` compose service so bktec's gotest runner has
+  # `go` on PATH (needed for `go list ./...` package discovery) and the
+  # Test Engine API token is forwarded (declared in docker-compose.yml).
+  # See TE-5828.
+  - name: ":test_tube: Collect commit metadata"
+    key: collect-commit-metadata
+    command: .buildkite/steps/collect-commit-metadata.sh
+    soft_fail: true
+    env:
+      BUILDKITE_TEST_ENGINE_SUITE_SLUG: buildkite-agent
+      BUILDKITE_TEST_ENGINE_TEST_RUNNER: gotest
+      # Test Engine API rejects parallelism = 0 even on metadata-only plan
+      # requests. See TE-5766 verification on bk/bk-rspec.
+      BUILDKITE_TEST_ENGINE_MAX_PARALLELISM: "2"
+      BUILDKITE_TEST_ENGINE_TARGET_TIME: "1m"
+    plugins:
+      - docker-compose#v4.14.0:
+          config: .buildkite/docker-compose.yml
+          cli-version: 2
+          propagate-environment: true
+          run: agent
+
   - group: ":go::scientist: Tests and Coverage"
     if_changed:
       - go.{mod,sum}

.buildkite/steps/collect-commit-metadata.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+# Collect git commit metadata via `bktec plan --collect-git-metadata`.
+#
+# This is a metadata-only side-channel for the buildkite-agent Test Engine
+# suite. The plan output is discarded -- the existing test steps continue to
+# use their declared `parallelism:` values unchanged. The only purpose of this
+# step is to ship commit / branch / diff metadata to the Test Engine plan
+# metadata pipeline on every build.
+#
+# See TE-5828 (and the bk/bk-rspec reference implementation in TE-5766) for
+# context. The step is soft-failed at the pipeline level so a Test Engine API
+# hiccup never blocks the build.
+#
+# Runs inside the `agent` docker-compose service (see
+# .buildkite/docker-compose.yml), which is a linux/amd64+arm64 golang image.
+# The service provides `go` on PATH for bktec's gotest runner (which shells
+# out to `go list ./...` to discover packages) and forwards
+# BUILDKITE_TEST_ENGINE_API_ACCESS_TOKEN into the container.
+#
+# bktec is downloaded fresh each run from the test-engine-client GitHub
+# release. The agent repo's go.mod pins test-engine-client v1.6.0 for use as
+# a `go tool` on the runtime test path; that v1 shape predates the `plan`
+# subcommand and is intentionally left untouched here. A future change should
+# unify both call sites on a single bktec version.
+
+set -euo pipefail
+
+BKTEC_VERSION="${BKTEC_VERSION:-2.5.0}"
+
+echo "+++ :test_tube: Installing bktec v${BKTEC_VERSION}"
+
+case "$(uname -m)" in
+  x86_64)         arch=amd64 ;;
+  aarch64|arm64)  arch=arm64 ;;
+  *)
+    echo "Unsupported architecture: $(uname -m)" >&2
+    exit 1
+    ;;
+esac
+
+bindir="$(mktemp -d)"
+url="https://github.com/buildkite/test-engine-client/releases/download/v${BKTEC_VERSION}/bktec_${BKTEC_VERSION}_linux_${arch}"
+
+curl --fail --silent --show-error --location --output "${bindir}/bktec" "${url}"
+chmod +x "${bindir}/bktec"
+export PATH="${bindir}:${PATH}"
+
+bktec --version
+
+echo "+++ :test_tube: Collecting git commit metadata via bktec plan (discarded)"
+
+# bktec needs a writable RESULT_PATH for plan output config validation. The
+# --json output is redirected to /dev/null below so this file is never read.
+export BUILDKITE_TEST_ENGINE_RESULT_PATH=/tmp/bktec-plan-metadata.json
+
+BKTEC_PREVIEW_SELECTION=1 bktec plan --json --collect-git-metadata > /dev/null
+
+echo "Plan request issued -- git commit metadata sent to Test Engine."