Promote un.rb to the default gems. It's preparation for 3.0.0-preview2.

doc/maintainers.rdoc

@@ -43,8 +43,6 @@ Zachary Scott (zzak)
 [lib/rubygems.rb, lib/rubygems/*]
   Eric Hodel (drbrain), Hiroshi SHIBATA (hsbt)
   https://github.com/rubygems/rubygems
-[lib/un.rb]
-  WATANABE Hirofumi (eban)
 [lib/unicode_normalize.rb, lib/unicode_normalize/*]
   Martin J. Dürst
 
@@ -262,6 +260,8 @@ Zachary Scott (zzak)
 [lib/tsort.rb]
   Tanaka Akira (akr)
   https://github.com/ruby/tsort
+[lib/un.rb]
+  WATANABE Hirofumi (eban)
 [lib/uri.rb, lib/uri/*]
   YAMADA, Akira (akira)
   https://github.com/ruby/uri

doc/standard_library.rdoc

@@ -11,7 +11,6 @@ description.
 MakeMakefile:: Module used to generate a Makefile for C extensions
 RbConfig:: Information of your configure and build of Ruby
 Gem:: Package management framework for Ruby
-un.rb:: Utilities to replace common UNIX commands
 
 == Extensions
 
@@ -78,6 +77,7 @@ Timeout:: Auto-terminate potentially long-running operations in Ruby
 tmpdir.rb:: Extends the Dir class to manage the OS temporary file path
 Tracer:: Outputs a source level execution trace of a Ruby program
 TSort:: Topological sorting using Tarjan's algorithm
+un.rb:: Utilities to replace common UNIX commands
 URI:: A Ruby module providing support for Uniform Resource Identifiers
 WEBrick:: An HTTP server toolkit for Ruby
 YAML:: Ruby client library for the Psych YAML implementation

lib/un.gemspec

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+Gem::Specification.new do |spec|
+  spec.name          = "un"
+  spec.version       = "0.1.0"
+  spec.authors       = ["WATANABE Hirofumi"]
+  spec.email         = ["eban@ruby-lang.org"]
+
+  spec.summary       = "Utilities to replace common UNIX commands"
+  spec.description   = spec.summary
+  spec.homepage      = "https://github.com/ruby/un"
+  spec.required_ruby_version = Gem::Requirement.new(">= 2.3.0")
+
+  spec.metadata["homepage_uri"] = spec.homepage
+  spec.metadata["source_code_uri"] = spec.homepage
+
+  spec.files = Dir.chdir(File.expand_path(__dir__)) do
+    `git ls-files -z`.split("\x0").reject { |f| f.match(%r{\A(?:test|spec|features)/}) }
+  end
+  spec.bindir        = "exe"
+  spec.executables   = spec.files.grep(%r{\Aexe/}) { |f| File.basename(f) }
+  spec.require_paths = ["lib"]
+end