[ruby/optparse] Define OptionParser::Version

https://github.com/ruby/optparse/commit/4c0021b5b2

lib/optparse.rb

@@ -419,6 +419,8 @@
 # have any questions, file a ticket at http://bugs.ruby-lang.org.
 #
 class OptionParser
+  OptionParser::Version = "0.1.0"
+
   # :stopdoc:
   NoArgument = [NO_ARGUMENT = :NONE, nil].freeze
   RequiredArgument = [REQUIRED_ARGUMENT = :REQUIRED, true].freeze

lib/optparse/optparse.gemspec

@@ -1,6 +1,14 @@
+name = File.basename(__FILE__, ".gemspec")
+version = nil
+["lib", ".."].find do |dir|
+  version = File.foreach(File.join(__dir__, dir, "#{name}.rb")) do |line|
+    /^\s*OptionParser::Version\s*=\s*"(.*)"/ =~ line and break $1
+  end rescue nil
+end
+
 Gem::Specification.new do |spec|
-  spec.name          = "optparse"
-  spec.version       = "0.1.0"
+  spec.name          = name
+  spec.version       = version
   spec.authors       = ["Nobu Nakada"]
   spec.email         = ["nobu@ruby-lang.org"]