[ruby/un] Expose UN::VERSION

https://github.com/ruby/un/commit/47bcad1804

lib/un.gemspec

@@ -1,8 +1,15 @@
 # frozen_string_literal: true
 
+name = File.basename(__FILE__, ".gemspec")
+version = ["lib", Array.new(name.count("-")+1).join("/")].find do |dir|
+  break File.foreach(File.join(__dir__, dir, "#{name.tr('-', '/')}.rb")) do |line|
+    /^\s*VERSION\s*=\s*"(.*)"/ =~ line and break $1
+  end rescue nil
+end
+
 Gem::Specification.new do |spec|
-  spec.name          = "un"
-  spec.version       = "0.2.1"
+  spec.name          = name
+  spec.version       = version
   spec.authors       = ["WATANABE Hirofumi"]
   spec.email         = ["eban@ruby-lang.org"]
 

lib/un.rb

@@ -412,6 +412,9 @@ def help
 end
 
 module UN # :nodoc:
+
+  VERSION = "0.2.1"
+
   module_function
   def help(argv, output: $stdout)
     all = argv.empty?