Forbid top level route sitemap

For the sitemap functionality we need to forbid the top level
route `sitemap` because it will be used later by our
controllers.

changelogs/unreleased/fj-forbid-top-level-route-sitemap.yml

+---
+title: Forbid top level route sitemap
+merge_request: 46677
+author:
+type: changed

db/post_migrate/20201102112206_rename_sitemap_namespace.rb

+# frozen_string_literal: true
+
+class RenameSitemapNamespace < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+  include Gitlab::Database::RenameReservedPathsMigration::V1
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  # We're taking over the /sitemap namespace
+  # since it's necessary for the default behavior of Sitemaps
+  def up
+    disable_statement_timeout do
+      rename_root_paths(['sitemap'])
+    end
+  end
+
+  def down
+    disable_statement_timeout do
+      revert_renames
+    end
+  end
+end

db/schema_migrations/20201102112206

+a861c91ebc7f7892020ba10a151df761b38bf69d5e02bcdf72a965eb266e6aff
\ No newline at end of file

doc/user/reserved_names.md

@@ -82,6 +82,7 @@ Currently the following names are reserved as top level groups:
 - `s`
 - `search`
 - `sent_notifications`
+- `sitemap`
 - `sitemap.xml`
 - `sitemap.xml.gz`
 - `slash-command-logo.png`

lib/gitlab/path_regex.rb

@@ -49,6 +49,7 @@ module Gitlab
       s
       search
       sent_notifications
+      sitemap
       sitemap.xml
       sitemap.xml.gz
       slash-command-logo.png

spec/lib/gitlab/path_regex_spec.rb

@@ -107,7 +107,7 @@ RSpec.describe Gitlab::PathRegex do
   end
 
   let(:sitemap_words) do
-    %w(sitemap.xml sitemap.xml.gz)
+    %w(sitemap sitemap.xml sitemap.xml.gz)
   end
 
   let(:ee_top_level_words) do
@@ -177,7 +177,7 @@ RSpec.describe Gitlab::PathRegex do
 
     # We ban new items in this list, see https://gitlab.com/gitlab-org/gitlab/-/issues/215362
     it 'does not allow expansion' do
-      expect(described_class::TOP_LEVEL_ROUTES.size).to eq(43)
+      expect(described_class::TOP_LEVEL_ROUTES.size).to eq(44)
     end
   end
 

spec/migrations/rename_sitemap_namespace_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20201102112206_rename_sitemap_namespace.rb')
+
+RSpec.describe RenameSitemapNamespace do
+  let(:namespaces) { table(:namespaces) }
+  let(:routes) { table(:routes) }
+  let(:sitemap_path) { 'sitemap' }
+
+  it 'correctly run #up and #down' do
+    create_namespace(sitemap_path)
+
+    reversible_migration do |migration|
+      migration.before -> {
+        expect(namespaces.pluck(:path)).to contain_exactly(sitemap_path)
+      }
+
+      migration.after -> {
+        expect(namespaces.pluck(:path)).to contain_exactly(sitemap_path + '0')
+      }
+    end
+  end
+
+  def create_namespace(path)
+    namespaces.create!(name: path, path: path).tap do |namespace|
+      routes.create!(path: namespace.path, name: namespace.name, source_id: namespace.id, source_type: 'Namespace')
+    end
+  end
+end