URI decode Page-Title header to preserve UTF-8 characters

app/assets/javascripts/repo/helpers/repo_helper.js

@@ -95,7 +95,7 @@ const RepoHelper = {
     return Service.getContent()
     .then((response) => {
       const data = response.data;
-      if (response.headers && response.headers['page-title']) data.pageTitle = response.headers['page-title'];
+      if (response.headers && response.headers['page-title']) data.pageTitle = decodeURI(response.headers['page-title']);
       if (response.headers && response.headers['is-root'] && !Store.isInitialRoot) {
         Store.isRoot = convertPermissionToBoolean(response.headers['is-root']);
         Store.isInitialRoot = Store.isRoot;

app/controllers/application_controller.rb

@@ -349,6 +349,6 @@ class ApplicationController < ActionController::Base
   def set_page_title_header
     # Per https://tools.ietf.org/html/rfc5987, headers need to be ISO-8859-1, not UTF-8
-    response.headers['Page-Title'] = page_title('GitLab').encode('ISO-8859-1')
+    response.headers['Page-Title'] = URI.escape(page_title('GitLab'))
   end
 end

spec/controllers/application_controller_spec.rb

@@ -221,6 +221,20 @@ describe ApplicationController do
     end
   end
+  describe '#set_page_title_header' do
+    let(:controller) { described_class.new }
+
+    it 'URI encodes UTF-8 characters in the title' do
+      response = double(headers: {})
+      allow_any_instance_of(PageLayoutHelper).to receive(:page_title).and_return('€100 · GitLab')
+      allow(controller).to receive(:response).and_return(response)
+
+      controller.send(:set_page_title_header)
+
+      expect(response.headers['Page-Title']).to eq('%E2%82%AC100%20%C2%B7%20GitLab')
+    end
+  end
+
   context 'two-factor authentication' do
     let(:controller) { described_class.new }