[CI] Add branch filtering logic to DRA trigger pipeline (elastic#127308)

This filtering will be used to trigger DRA for 7.17 weekly instead of
twice a day.

Author: jozala

.buildkite/scripts/dra-workflow.trigger.sh

@@ -2,10 +2,34 @@
 
 set -euo pipefail
 
-echo "steps:"
-
 source .buildkite/scripts/branches.sh
 
+# We use that filtering to keep different schedule for different branches
+if [ -n "${INCLUDED_BRANCHES:-}" ]; then
+  # If set, only trigger the pipeline for the specified branches
+  IFS=',' read -r -a BRANCHES <<< "${INCLUDED_BRANCHES}"
+elif [ -n "${EXCLUDED_BRANCHES:-}" ]; then
+  # If set, listed branches will be excluded from the list of branches in branches.json
+  IFS=',' read -r -a EXCLUDED_BRANCHES <<< "${EXCLUDED_BRANCHES}"
+  FILTERED_BRANCHES=()
+    for BRANCH in "${BRANCHES[@]}"; do
+      EXCLUDE=false
+      for EXCLUDED_BRANCH in "${EXCLUDED_BRANCHES[@]}"; do
+        if [ "$BRANCH" == "$EXCLUDED_BRANCH" ]; then
+          EXCLUDE=true
+          break
+        fi
+      done
+      if [ "$EXCLUDE" = false ]; then
+        FILTERED_BRANCHES+=("$BRANCH")
+      fi
+    done
+    BRANCHES=("${FILTERED_BRANCHES[@]}")
+fi
+
+
+echo "steps:"
+
 for BRANCH in "${BRANCHES[@]}"; do
   INTAKE_PIPELINE_SLUG="elasticsearch-intake"
   BUILD_JSON=$(curl -sH "Authorization: Bearer ${BUILDKITE_API_TOKEN}" "https://api.buildkite.com/v2/organizations/elastic/pipelines/${INTAKE_PIPELINE_SLUG}/builds?branch=${BRANCH}&state=passed&per_page=1" | jq '.[0] | {commit: .commit, url: .web_url}')