Create forward port issues for merges into main

This reverts commit 4e884b27f874ff210d0435fca176c75eff38b166.

Closes gh-31148

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"
-    return nil
+    current_branch = $main_branch
   end
   rewritten_message = ""
   message = File.read(message_file)
@@ -68,6 +68,4 @@ 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