exit if promotion was triggered from a non-release-looking branch

Author: delanni

.buildkite/scripts/steps/es_snapshots/trigger_promote.sh

@@ -9,6 +9,13 @@ set -euo pipefail
 
 export ES_SNAPSHOT_MANIFEST="${ES_SNAPSHOT_MANIFEST:-"$(buildkite-agent meta-data get ES_SNAPSHOT_MANIFEST)"}"
 
+if [[ "${BUILDKITE_BRANCH:-}" =~ ^(main|\d+\.\d+)$ ]] || [[ "${FORCE_PROMOTE:-}" =~ ^(1|true)$ ]]; then
+  echo "Promoting snapshots on branch: ${BUILDKITE_BRANCH}"
+else
+  echo "ES Promotion is not allowed on feature branch ${BUILDKITE_BRANCH}"
+  exit 0
+fi
+
 cat << EOF | buildkite-agent pipeline upload
 steps:
   - trigger: 'kibana-elasticsearch-snapshot-promote'