Vendor tsort into rubygems

So that it loads a consistent version of the library and `rubygems` is
never affected by gem activation conflicts related to `tsort`.

Getting CI green required updating one `bundler` spec, because `tsort`
is no longer loaded by `bundle clean` until after `BUNDLE_PATH` has been
changed, so to ensure it is found, it needs to be installed under
`BUNDLE_PATH` as well (which will be different from the global system
path on Bundler 3, meaning installing `tsort` to the global system path
is not enough there). This spec workaround can be removed once we also
vendor `tsort` inside `bundler`.

.rubocop.yml

@@ -5,6 +5,7 @@ AllCops:
   Exclude:
     - 'bundler/**/*'
     - 'lib/rubygems/resolver/molinillo/**/*'
+    - 'lib/rubygems/tsort/**/*'
     - 'pkg/**/*'
     - 'tmp/**/*'
   TargetRubyVersion: 2.3

Manifest.txt

@@ -494,6 +494,9 @@ lib/rubygems/ssl_certs/rubygems.org/GlobalSignRootCA.pem
 lib/rubygems/ssl_certs/rubygems.org/GlobalSignRootCA_R3.pem
 lib/rubygems/stub_specification.rb
 lib/rubygems/text.rb
+lib/rubygems/tsort.rb
+lib/rubygems/tsort/LICENSE.txt
+lib/rubygems/tsort/lib/tsort.rb
 lib/rubygems/uninstaller.rb
 lib/rubygems/unknown_command_spell_checker.rb
 lib/rubygems/uri.rb

Rakefile

@@ -79,6 +79,16 @@ if File.exist?("util/automatiek.rake")
     lib.vendor_lib = "lib/rubygems/resolver/molinillo"
     lib.license_path = "LICENSE"
   end
+
+  desc "Vendor a specific version of tsort"
+  Automatiek::RakeTask.new("tsort") do |lib|
+    lib.version = "master"
+    lib.download = { :github => "https://github.com/ruby/tsort" }
+    lib.namespace = "TSort"
+    lib.prefix = "Gem"
+    lib.vendor_lib = "lib/rubygems/tsort"
+    lib.license_path = "LICENSE.txt"
+  end
 end
 
 namespace :rubocop do

bundler/spec/commands/clean_spec.rb

@@ -644,6 +644,8 @@ def should_not_have_gems(*gems)
       source "#{file_uri_for(gem_repo2)}"
     G
 
+    realworld_system_gems "tsort --version 0.1.0", :path => default_bundle_path
+
     bundle "clean --force", :env => { "BUNDLER_GEM_DEFAULT_DIR" => system_gem_path.to_s }
 
     expect(out).not_to include("Removing irb")

lib/rubygems/dependency_list.rb

@@ -5,7 +5,7 @@
 # See LICENSE.txt for permissions.
 #++
 
-require 'tsort'
+require_relative 'tsort'
 require_relative 'deprecate'
 
 ##
@@ -20,7 +20,7 @@ class Gem::DependencyList
   attr_reader :specs
 
   include Enumerable
-  include TSort
+  include Gem::TSort
 
   ##
   # Allows enabling/disabling use of development dependencies

lib/rubygems/request_set.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
-require 'tsort'
+require_relative 'tsort'
 
 ##
 # A RequestSet groups a request to activate a set of dependencies.
@@ -15,7 +15,7 @@
 #   #=> ["nokogiri-1.6.0", "mini_portile-0.5.1", "pg-0.17.0"]
 
 class Gem::RequestSet
-  include TSort
+  include Gem::TSort
 
   ##
   # Array of gems to install even if already installed

lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'tsort'
+require_relative '../../../../tsort'
 
 require_relative 'dependency_graph/log'
 require_relative 'dependency_graph/vertex'
@@ -17,7 +17,7 @@ def each
       vertices.values.each { |v| yield v }
     end
 
-    include TSort
+    include Gem::TSort
 
     # @!visibility private
     alias tsort_each_node each

lib/rubygems/tsort.rb

@@ -0,0 +1,3 @@
+# frozen_string_literal: true
+
+require_relative 'tsort/lib/tsort'

lib/rubygems/tsort/LICENSE.txt

@@ -0,0 +1,22 @@
+Copyright (C) 1993-2013 Yukihiro Matsumoto. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+1. Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.