Add rdoc and test of Encoding#replicate.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@26068 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

encoding.c

@@ -313,6 +313,15 @@ rb_enc_replicate(const char *name, rb_encoding *encoding)
     return idx;
 }
 
+/*
+ * call-seq:
+ *   enc.replicate(name) => encoding
+ *
+ * Returns a replicated encoding of _enc whose name is _name_.
+ * The new encoding should have the same byte structure of _enc_.
+ * If _name_ is used by another encoding, raise ArgumentError.
+ *
+ */
 static VALUE
 enc_replicate(VALUE encoding, VALUE name)
 {

test/ruby/test_encoding.rb

@@ -51,6 +51,11 @@ class TestEncoding < Test::Unit::TestCase
     end
   end
 
+  def test_replicate
+    assert(Encoding::UTF_8.replicate('UTF-8-ANOTHER'))
+    assert(Encoding::ISO_2022_JP.replicate('ISO-2022-JP-ANOTHER'))
+  end
+
   def test_dummy_p
     assert_equal(true, Encoding::ISO_2022_JP.dummy?)
     assert_equal(false, Encoding::UTF_8.dummy?)