Add FwC branch configuration and update periodic trigger logic

Ensuring that only relevant branches are considered.

Author: jozala

.buildkite/scripts/fwc-branches.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# Configure FwC test branches
+# We do not want 7.x branch and only to run for branches that:
+# - have released at least one minor version (not main)
+# - have previous minor unreleased (not the oldest development branch)
+FWC_BRANCHES=()
+for branch in "${BRANCHES[@]}"; do
+  if [[ ! "$branch" =~ ^7\..* ]]; then
+    FWC_BRANCHES+=("$branch")
+  fi
+done
+# Remove first and last element
+FWC_BRANCHES=("${FWC_BRANCHES[@]:1:${#FWC_BRANCHES[@]}-2}")
+
+shouldRunFwcFor() {
+  local branch=$1
+  for fwc_branch in "${FWC_BRANCHES[@]}"; do
+    if [[ "$fwc_branch" == "$branch" ]]; then
+      return 0
+    fi
+  done
+  return 1
+}

.buildkite/scripts/periodic.trigger.sh

@@ -5,6 +5,7 @@ set -euo pipefail
 echo "steps:"
 
 source .buildkite/scripts/branches.sh
+source .buildkite/scripts/fwc-branches.sh
 
 IS_FIRST=true
 SKIP_DELAY="${SKIP_DELAY:-false}"
@@ -46,8 +47,7 @@ EOF
       branch: "$BRANCH"
       commit: "$LAST_GOOD_COMMIT"
 EOF
-# Include forward compatibility tests only for the bugfix branch
-if [[ "${BRANCH}" == "${BRANCHES[2]}" ]]; then
+if shouldRunFwcFor "$BRANCH"; then
   cat <<EOF
   - trigger: elasticsearch-periodic-fwc
     label: Trigger periodic-fwc pipeline for $BRANCH