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/core/string/hex_spec.rb

@@ -0,0 +1,49 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../fixtures/classes.rb', __FILE__)
+
+# TODO: Move actual results to String#to_int() and spec in terms of it
+describe "String#hex" do
+  it "treats leading characters of self as a string of hex digits" do
+    "0a".hex.should == 10
+    "0o".hex.should == 0
+    "0x".hex.should == 0
+    "A_BAD_BABE".hex.should == 0xABADBABE
+    "0b1010".hex.should == "b1010".hex
+    "0d500".hex.should == "d500".hex
+    "abcdefG".hex.should == 0xabcdef
+  end
+
+  it "does not accept a sequence of underscores as part of a number" do
+    "a__b".hex.should == 0xa
+    "a____b".hex.should == 0xa
+    "a___f".hex.should == 0xa
+  end
+
+  it "takes an optional sign" do
+    "-1234".hex.should == -4660
+    "+1234".hex.should == 4660
+  end
+
+  it "takes an optional 0x" do
+    "0x0a".hex.should == 10
+    "0a".hex.should == 10
+  end
+
+  it "requires that the sign is in front of the 0x if present" do
+    "-0x1".hex.should == -1
+    "0x-1".hex.should == 0
+  end
+
+  it "returns 0 on error" do
+    "".hex.should == 0
+    "+-5".hex.should == 0
+    "wombat".hex.should == 0
+    "0x0x42".hex.should == 0
+  end
+
+  it "returns 0 if sequence begins with underscore" do
+    "_a".hex.should == 0
+    "___b".hex.should == 0
+    "___0xc".hex.should == 0
+  end
+end