Add e2e test of push via HTTP via Git protocol v2

Adds a new end-to-end test to check that Git protocol v2 can be used to
push over HTTP

qa/qa/specs/features/browser_ui/3_create/repository/protocol_v2_push_http_spec.rb

+# frozen_string_literal: true
+
+module QA
+  context 'Create' do
+    describe 'Push over HTTP using Git protocol version 2', :requires_git_protocol_v2 do
+      it 'user pushes to the repository' do
+        Runtime::Browser.visit(:gitlab, Page::Main::Login)
+        Page::Main::Login.perform(&:sign_in_using_credentials)
+
+        # Create a project to push to
+        project = Resource::Project.fabricate! do |project|
+          project.name = 'git-protocol-project'
+        end
+
+        file_name = 'README.md'
+        file_content = 'Test Git protocol v2'
+        git_protocol = '2'
+        git_protocol_reported = nil
+
+        # Use Git to clone the project, push a file to it, and then check the
+        # supported Git protocol
+        Git::Repository.perform do |repository|
+          username = 'GitLab QA'
+          email = 'root@gitlab.com'
+
+          repository.uri = project.repository_http_location.uri
+          repository.use_default_credentials
+          repository.clone
+          repository.configure_identity(username, email)
+
+          git_protocol_reported = repository.push_with_git_protocol(
+            git_protocol,
+            file_name,
+            file_content)
+        end
+
+        project.visit!
+        Page::Project::Show.perform(&:wait_for_push)
+
+        # Check that the push worked
+        expect(page).to have_content(file_name)
+        expect(page).to have_content(file_content)
+
+        # And check that the correct Git protocol was used
+        expect(git_protocol_reported).to eq(git_protocol)
+      end
+    end
+  end
+end