Always use origin for checking if the heads point to the same commit

lib/fastlane/plugin/wpmreleasetoolkit/actions/common/create_release_backmerge_pull_request_action.rb

@@ -25,7 +25,7 @@ def self.run(params)
         github_helper = Fastlane::Helper::GithubHelper.new(github_token: params[:github_token])
         target_milestone = milestone_title.nil? ? nil : github_helper.get_milestone(repository, milestone_title)
 
-        Git.open(Dir.pwd).fetch('origin')
+        Git.open(Dir.pwd).fetch
 
         final_target_branches = if target_branches.empty?
                                   unless source_branch.start_with?('release/')
@@ -105,7 +105,10 @@ def self.create_backmerge_pr(token:, repository:, title:, head_branch:, base_bra
         # if there's a callback, make sure it didn't switch branches
         other_action.ensure_git_branch(branch: "^#{intermediate_branch}/") unless intermediate_branch_created_callback.nil?
 
-        if Fastlane::Helper::GitHelper.point_to_same_commit?(base_branch, head_branch)
+        base_branch_ref = "origin/#{base_branch}" unless base_branch.start_with?('origin/')
+        head_branch_ref = "origin/#{head_branch}" unless head_branch.start_with?('origin/')
+
+        if Fastlane::Helper::GitHelper.point_to_same_commit?(base_branch_ref, head_branch_ref)
           UI.error("No differences between #{head_branch} and #{base_branch}. Skipping PR creation.")
           return nil
         end