Replace filelist for git ls-files result.

Author: hsbt

fileutils.gemspec

@@ -6,7 +6,7 @@ Gem::Specification.new do |s|
   s.description = "Several file utility methods for copying, moving, removing, etc."
 
   s.require_path = %w{lib}
-  s.files = %w{fileutils.rb}
+  s.files = [".gitignore", ".travis.yml", "Gemfile", "LICENSE.txt", "README.md", "Rakefile", "bin/console", "bin/setup", "fileutils.gemspec", "lib/fileutils.rb"]
   s.required_ruby_version = ">= 2.5.0dev"
 
   s.authors = ["Minero Aoki"]