Add command-line specs for --enable-frozen-string-literal.

Author: chrisseaton

command_line/fixtures/freeze_flag_across_files.rb

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+require_relative 'freeze_flag_required'
+
+p "abc".freeze.object_id == $second_literal_id

command_line/fixtures/freeze_flag_across_files_diff_enc.rb

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+require_relative 'freeze_flag_required_diff_enc'
+
+p "abc".freeze.object_id != $second_literal_id

command_line/fixtures/freeze_flag_one_literal.rb

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+ids = Array.new(2) { "abc".freeze.object_id }
+p ids.first == ids.last

command_line/fixtures/freeze_flag_required.rb

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+$second_literal_id = "abc".freeze.object_id

command_line/fixtures/freeze_flag_required_diff_enc.rb

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+p "abc".freeze.object_id == "abc".freeze.object_id

command_line/fixtures/freeze_flag_two_literals.rb

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+require File.expand_path('../../spec_helper', __FILE__)
+
+describe "The --enable-frozen-string-literal flag causes string literals to" do
+
+  it "produce the same object each time" do
+    ruby_exe(fixture(__FILE__, "freeze_flag_one_literal.rb"), options: "--enable-frozen-string-literal").chomp.should == "true"
+  end
+
+  it "produce the same object for literals with the same content" do
+    ruby_exe(fixture(__FILE__, "freeze_flag_two_literals.rb"), options: "--enable-frozen-string-literal").chomp.should == "true"
+  end
+
+  it "produce the same object for literals with the same content in different files" do
+    ruby_exe(fixture(__FILE__, "freeze_flag_across_files.rb"), options: "--enable-frozen-string-literal").chomp.should == "true"
+  end
+
+  it "produce different objects for literals with the same content in different files if they have different encodings" do
+    ruby_exe(fixture(__FILE__, "freeze_flag_across_files_diff_enc.rb"), options: "--enable-frozen-string-literal").chomp.should == "true"
+  end
+
+end