Merge bundler to standard libraries.

rubygems 2.7.x depends bundler-1.15.x. This is preparation for
  rubygems and bundler migration.

  * lib/bundler.rb, lib/bundler/*: files of bundler-1.15.4
  * spec/bundler/*: rspec examples of bundler-1.15.4. I applied patches.
    * https://github.com/bundler/bundler/pull/6007
    * Exclude not working examples on ruby repository.
    * Fake ruby interpriter instead of installed ruby.
  * Makefile.in: Added test task named `test-bundler`. This task is only
    working macOS/linux yet. I'm going to support Windows environment later.
  * tool/sync_default_gems.rb: Added sync task for bundler.

  [Feature #12733][ruby-core:77172]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59779 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/bundler/commands/licenses_spec.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+require "spec_helper"
+
+RSpec.describe "bundle licenses" do
+  before :each do
+    install_gemfile <<-G
+      source "file://#{gem_repo1}"
+      gem "rails"
+      gem "with_license"
+    G
+  end
+
+  it "prints license information for all gems in the bundle" do
+    bundle "licenses"
+
+    expect(out).to include("bundler: Unknown")
+    expect(out).to include("with_license: MIT")
+  end
+
+  it "performs an automatic bundle install" do
+    gemfile <<-G
+      source "file://#{gem_repo1}"
+      gem "rails"
+      gem "with_license"
+      gem "foo"
+    G
+
+    bundle "config auto_install 1"
+    bundle :licenses
+    expect(out).to include("Installing foo 1.0")
+  end
+end