Unify check branch name exist

app/controllers/projects/application_controller.rb

@@ -74,7 +74,7 @@ class Projects::ApplicationController < ApplicationController
   end
 
   def require_branch_head
-    unless @repository.branch_names.include?(@ref)
+    unless @repository.branch_exists?(@ref)
       redirect_to(
         namespace_project_tree_path(@project.namespace, @project, @ref),
         notice: "This action is not allowed unless you are on a branch"

app/helpers/application_helper.rb

@@ -116,7 +116,7 @@ module ApplicationHelper
     return false if project.merge_requests.where(source_branch: event.branch_name).opened.any?
 
     # Skip if user removed branch right after that
-    return false unless project.repository.branch_names.include?(event.branch_name)
+    return false unless project.repository.branch_exists?(event.branch_name)
 
     true
   end

app/helpers/branches_helper.rb

@@ -10,7 +10,7 @@ module BranchesHelper
   end
 
   def can_push_branch?(project, branch_name)
-    return false unless project.repository.branch_names.include?(branch_name)
+    return false unless project.repository.branch_exists?(branch_name)
 
     ::Gitlab::GitAccess.new(current_user, project).can_push_to_branch?(branch_name)
   end

app/models/repository.rb

@@ -192,7 +192,7 @@ class Repository
   end
 
   def branch_names
-    cache.fetch(:branch_names) { branches.map(&:name) }
+    @branch_names ||= cache.fetch(:branch_names) { branches.map(&:name) }
   end
 
   def branch_exists?(branch_name)
@@ -267,6 +267,7 @@ class Repository
 
   def expire_branches_cache
     cache.expire(:branch_names)
+    @branch_names = nil
     @local_branches = nil
   end
 
@@ -332,10 +333,6 @@ class Repository
     @lookup_cache ||= {}
   end
 
-  def expire_branch_names
-    cache.expire(:branch_names)
-  end
-
   def expire_avatar_cache(branch_name = nil, revision = nil)
     # Avatars are pulled from the default branch, thus if somebody pushes to a
     # different branch there's no need to expire anything.

app/models/user.rb

@@ -487,9 +487,8 @@ class User < ActiveRecord::Base
     events.recent.find do |event|
       project = Project.find_by_id(event.project_id)
       next unless project
-      repo = project.repository
 
-      if repo.branch_names.include?(event.branch_name)
+      if project.repository.branch_exists?(event.branch_name)
         merge_requests = MergeRequest.where("created_at >= ?", event.created_at).
             where(source_project_id: project.id,
                   source_branch: event.branch_name)

spec/workers/merge_worker_spec.rb

@@ -9,7 +9,7 @@ describe MergeWorker do
 
     before do
       source_project.team << [author, :master]
-      source_project.repository.expire_branch_names
+      source_project.repository.expire_branches_cache
     end
 
     it 'clears cache of source repo after removing source branch' do