use regex for filter

util/jenkins/get-rc-branches.sh

@@ -62,7 +62,7 @@ fi
 
 $noop cd "/var/tmp/$repo_basename"
 if [[ -z $noop ]]; then
-    for branch in $(git branch -a | grep "$filter" | sort -r | tr -d ' '); do
+    for branch in $(git branch -a | sort -r | tr -d ' ' | grep -P "$filter" ); do
       echo "origin/${branch}"
     done
 else