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

1 files changed, 38 insertions, 0 deletions

diff --git a/lib/bundler/environment_preserver.rb b/lib/bundler/environment_preserver.rb
new file mode 100644
index 0000000000..a891f4854d
--- /dev/null
+++ b/lib/bundler/environment_preserver.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+module Bundler
+  class EnvironmentPreserver
+    # @param env [ENV]
+    # @param keys [Array<String>]
+    def initialize(env, keys)
+      @original = env.to_hash
+      @keys = keys
+      @prefix = "BUNDLER_ORIG_"
+    end
+
+    # @return [Hash]
+    def backup
+      env = @original.clone
+      @keys.each do |key|
+        value = env[key]
+        original_value = env[@prefix + key]
+        if !value.nil? && !value.empty? && original_value.nil?
+          env[@prefix + key] = value
+        end
+      end
+      env
+    end
+
+    # @return [Hash]
+    def restore
+      env = @original.clone
+      @keys.each do |key|
+        value_original = env[@prefix + key]
+        unless value_original.nil? || value_original.empty?
+          env[key] = value_original
+          env.delete(@prefix + key)
+        end
+      end
+      env
+    end
+  end
+end