[rubygems/rubygems] Add `gem env user_gemhome` and `gem env user_gemdir`

https://github.com/rubygems/rubygems/commit/14d3f80df6

lib/rubygems/commands/environment_command.rb

@@ -10,6 +10,7 @@ class Gem::Commands::EnvironmentCommand < Gem::Command
     args = <<-EOF
           home            display the path where gems are installed. Aliases: gemhome, gemdir, GEM_HOME
           path            display path used to search for gems. Aliases: gempath, GEM_PATH
+          user_gemhome    display the path where gems are installed when `--user-install` is given. Aliases: user_gemdir
           version         display the gem format version
           remotesources   display the remote gem servers
           platform        display the supported gem platforms
@@ -80,6 +81,8 @@ lib/rubygems/defaults/operating_system.rb
         Gem.dir
       when /^gempath/, /^path/, /^GEM_PATH/ then
         Gem.path.join(File::PATH_SEPARATOR)
+      when /^user_gemdir/, /^user_gemhome/ then
+        Gem.user_dir
       when /^remotesources/ then
         Gem.sources.to_a.join("\n")
       when /^platform/ then

test/rubygems/test_gem_commands_environment_command.rb

@@ -65,6 +65,28 @@ class TestGemCommandsEnvironmentCommand < Gem::TestCase
     assert_equal '', @ui.error
   end
 
+  def test_execute_user_gemdir
+    @cmd.send :handle_options, %w[user_gemdir]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    assert_equal "#{Gem.user_dir}\n", @ui.output
+    assert_equal '', @ui.error
+  end
+
+  def test_execute_user_gemhome
+    @cmd.send :handle_options, %w[user_gemhome]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    assert_equal "#{Gem.user_dir}\n", @ui.output
+    assert_equal '', @ui.error
+  end
+
   def test_execute_gempath
     @cmd.send :handle_options, %w[gempath]