Fix inconsistent number of branches when remote branches are present

Users of project mirrors would see that the number of branches did not
match the number in the branch dropdown because remote branches were
counted when Rugged was in use. With Gitaly, only local branches
are counted.

Closes #36934

lib/gitlab/git/repository.rb

@@ -153,7 +153,7 @@ module Gitlab
           if is_enabled
             gitaly_ref_client.count_branch_names
           else
-            rugged.branches.count do |ref|
+            rugged.branches.each(:local).count do |ref|
               begin
                 ref.name && ref.target # ensures the branch is valid
 

spec/lib/gitlab/git/repository_spec.rb

@@ -977,6 +977,36 @@ describe Gitlab::Git::Repository, seed_helper: true do
     it 'returns the number of branches' do
       expect(repository.branch_count).to eq(10)
     end
+
+    context 'with local and remote branches' do
+      let(:repository) do
+        Gitlab::Git::Repository.new('default', File.join(TEST_MUTABLE_REPO_PATH, '.git'))
+      end
+
+      before do
+        create_remote_branch(repository, 'joe', 'remote_branch', 'master')
+        repository.create_branch('local_branch', 'master')
+      end
+
+      after do
+        FileUtils.rm_rf(TEST_MUTABLE_REPO_PATH)
+        ensure_seeds
+      end
+
+      it 'returns the count of local branches' do
+        expect(repository.branch_count).to eq(repository.local_branches.count)
+      end
+
+      context 'with Gitaly disabled' do
+        before do
+          allow(Gitlab::GitalyClient).to receive(:feature_enabled?).and_return(false)
+        end
+
+        it 'returns the count of local branches' do
+          expect(repository.branch_count).to eq(repository.local_branches.count)
+        end
+      end
+    end
   end
 
   describe "#ls_files" do