Add in-tree mspec and ruby/spec

* For easier modifications of ruby/spec by MRI developers.
* .gitignore: track changes under spec.
* spec/mspec, spec/rubyspec: add in-tree mspec and ruby/spec.
  These files can therefore be updated like any other file in MRI.
  Instructions are provided in spec/README.
  [Feature #13156] [ruby-core:79246]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58595 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/rubyspec/command_line/dash_upper_u_spec.rb

@@ -0,0 +1,41 @@
+describe "ruby -U" do
+  it "sets Encoding.default_internal to UTF-8" do
+     ruby_exe('print Encoding.default_internal.name',
+              options: '-U').should == 'UTF-8'
+  end
+
+  it "does nothing different if specified multiple times" do
+     ruby_exe('print Encoding.default_internal.name',
+              options: '-U -U').should == 'UTF-8'
+  end
+
+  it "is overruled by Encoding.default_internal=" do
+     ruby_exe('Encoding.default_internal="ascii"; print Encoding.default_internal.name',
+              options: '-U').should == 'US-ASCII'
+  end
+
+  it "does not affect the default external encoding" do
+     ruby_exe('Encoding.default_external="ascii"; print Encoding.default_external.name',
+              options: '-U').should == 'US-ASCII'
+  end
+
+  it "does not affect the source encoding" do
+     ruby_exe("print __ENCODING__.name",
+              options: '-U -KE').should == 'EUC-JP'
+     ruby_exe("print __ENCODING__.name",
+              options: '-KE -U').should == 'EUC-JP'
+  end
+
+  # I assume IO redirection will break on Windows...
+  it "raises a RuntimeError if used with -Eext:int" do
+    ruby_exe("p 1",
+             options: '-U -Eascii:ascii',
+             args: '2>&1').should =~ /RuntimeError/
+  end
+
+  it "raises a RuntimeError if used with -E:int" do
+    ruby_exe("p 1",
+             options: '-U -E:ascii',
+             args: '2>&1').should =~ /RuntimeError/
+  end
+end