pr.rb in circleci-bundle-update-pr-1.14.3

- old
+ new

@@ -30,10 +30,10 @@
           update_pull_request_body(pull_request[:number])
           add_assignees(pull_request[:number], assignees) if assignees
           request_review(pull_request[:number], reviewers) if reviewers
         end
 
-        BRANCH_PREFIX = 'bundle-update-'.freeze
+        BRANCH_PREFIX = ENV['BRANCH_PREFIX'] || 'bundle-update-'.freeze
         TITLE_PREFIX = 'bundle update at '.freeze
 
         def self.raise_if_env_unvalid!
           raise "$CIRCLE_PROJECT_USERNAME isn't set" unless ENV['CIRCLE_PROJECT_USERNAME']
           raise "$CIRCLE_PROJECT_REPONAME isn't set" unless ENV['CIRCLE_PROJECT_REPONAME']