Call after_create_branch in Repository#add_branch

This ensures the right caches are flushed when adding a branch via the
UI, instead of only flushing this one random cache.

app/models/repository.rb

@@ -133,7 +133,7 @@ class Repository
       rugged.branches.create(branch_name, target)
     end
 
-    expire_branches_cache
+    after_create_branch
     find_branch(branch_name)
   end
 
@@ -356,6 +356,7 @@ class Repository
 
   # Runs code after a new branch has been created.
   def after_create_branch
+    expire_branches_cache
     expire_has_visible_content_cache
     expire_branch_count_cache
   end

spec/models/repository_spec.rb

@@ -148,6 +148,12 @@ describe Repository, models: true do
 
         expect(branch.name).to eq('new_feature')
       end
+
+      it 'calls the after_create_branch hook' do
+        expect(repository).to receive(:after_create_branch)
+
+        repository.add_branch(user, 'new_feature', 'master')
+      end
     end
 
     context 'when pre hooks failed' do