Hide related branches when user does not have permission

Guest user of a project should not see branches

app/assets/javascripts/issue.js

@@ -16,7 +16,9 @@ export default class Issue {
     Issue.createMrDropdownWrap = document.querySelector('.create-mr-dropdown-wrap');
 
     Issue.initMergeRequests();
+    if (document.querySelector('#related-branches')) {
       Issue.initRelatedBranches();
+    }
 
     this.closeButtons = $('a.btn-close');
     this.reopenButtons = $('a.btn-reopen');

app/controllers/projects/issues_controller.rb

@@ -39,6 +39,7 @@ class Projects::IssuesController < Projects::ApplicationController
   before_action :authorize_create_merge_request_from!, only: [:create_merge_request]
 
   before_action :authorize_import_issues!, only: [:import_csv]
+  before_action :authorize_download_code!, only: [:related_branches]
 
   before_action :set_suggested_issues_feature_flags, only: [:new]
 

app/views/projects/issues/show.html.haml

@@ -80,6 +80,7 @@
     #merge-requests{ data: { url: referenced_merge_requests_project_issue_path(@project, @issue) } }
       // This element is filled in using JavaScript.
 
+    - if can?(current_user, :download_code, @project)
       #related-branches{ data: { url: related_branches_project_issue_path(@project, @issue) } }
         // This element is filled in using JavaScript.
 

changelogs/unreleased/security-56224.yml

+---
+title: Hide "related branches" when user does not have permission
+merge_request:
+author:
+type: security

spec/features/issues/user_creates_branch_and_merge_request_spec.rb

 require 'rails_helper'
 
 describe 'User creates branch and merge request on issue page', :js do
+  let(:membership_level) { :developer }
   let(:user) { create(:user) }
   let!(:project) { create(:project, :repository) }
   let(:issue) { create(:issue, project: project, title: 'Cherry-Coloured Funk') }
@@ -17,7 +18,7 @@ describe 'User creates branch and merge request on issue page', :js do
 
   context 'when signed in' do
     before do
-      project.add_developer(user)
+      project.add_user(user, membership_level)
 
       sign_in(user)
     end
@@ -167,6 +168,39 @@ describe 'User creates branch and merge request on issue page', :js do
         expect(page).not_to have_css('.create-mr-dropdown-wrap')
       end
     end
+
+    context 'when related branch exists' do
+      let!(:project) { create(:project, :repository, :private) }
+      let(:branch_name) { "#{issue.iid}-foo" }
+
+      before do
+        project.repository.create_branch(branch_name, 'master')
+
+        visit project_issue_path(project, issue)
+      end
+
+      context 'when user is developer' do
+        it 'shows related branches' do
+          expect(page).to have_css('#related-branches')
+
+          wait_for_requests
+
+          expect(page).to have_content(branch_name)
+        end
+      end
+
+      context 'when user is guest' do
+        let(:membership_level) { :guest }
+
+        it 'does not show related branches' do
+          expect(page).not_to have_css('#related-branches')
+
+          wait_for_requests
+
+          expect(page).not_to have_content(branch_name)
+        end
+      end
+    end
   end
 
   private