Don't create forward port issues for merges into main

git/hooks/prepare-forward-merge

@@ -27,7 +27,7 @@ end
 def rewrite_message(message_file, fixed)
   current_branch = `git rev-parse --abbrev-ref HEAD`.strip
   if current_branch == "main"
-    current_branch = $main_branch
+    return nil
   end
   rewritten_message = ""
   message = File.read(message_file)
@@ -68,4 +68,6 @@ end
 $log.debug "Searching for for forward merge"
 fixed = get_fixed_issues()
 rewritten_message = rewrite_message(message_file, fixed)
+unless rewritten_message.nil?
   File.write(message_file, rewritten_message)
+end