[ruby/reline] @convert_meta is true unless 8-bit characters

If Reline::IOGate.encoding contains 7-bit characters, convert-meta will set it On.

Because in readline(3):

>  The default is On, but readline will set it to Off if the locale contains eight-bit characters.

As far as I know, 7-bit encoding used in terminals is only US-ASCII.

https://github.com/ruby/reline/commit/b71d1fa496

lib/reline/config.rb

@@ -67,6 +67,7 @@ class Reline::Config
     @keyseq_timeout = 500
     @test_mode = false
     @autocompletion = false
+    @convert_meta = true if seven_bit_encoding?(Reline::IOGate.encoding)
   end
 
   def reset
@@ -387,4 +388,8 @@ class Reline::Config
     end
     ret
   end
+
+  private def seven_bit_encoding?(encoding)
+    encoding == Encoding::US_ASCII
+  end
 end

test/reline/test_config.rb

@@ -11,12 +11,14 @@ class Reline::Config::Test < Reline::TestCase
       Dir.mkdir(@tmpdir)
     end
     Dir.chdir(@tmpdir)
+    Reline.test_mode
     @config = Reline::Config.new
   end
 
   def teardown
     Dir.chdir(@pwd)
     FileUtils.rm_rf(@tmpdir)
+    Reline.test_reset
     @config.reset
   end
 
@@ -81,6 +83,22 @@ class Reline::Config::Test < Reline::TestCase
     assert_equal '(Emacs)', @config.instance_variable_get(:@emacs_mode_string)
   end
 
+  def test_encoding_is_ascii
+    @config.reset
+    Reline::IOGate.reset(encoding: Encoding::US_ASCII)
+    @config = Reline::Config.new
+
+    assert_equal true, @config.convert_meta
+  end
+
+  def test_encoding_is_not_ascii
+    @config.reset
+    Reline::IOGate.reset(encoding: Encoding::UTF_8)
+    @config = Reline::Config.new
+
+    assert_equal nil, @config.convert_meta
+  end
+
   def test_comment_line
     @config.read_lines([" #a: error\n"])
     assert_not_include @config.key_bindings, nil