Extract gemspec and removed needless files

rake.gemspec

@@ -30,8 +30,68 @@ Rake has the following features:
     "source_code_uri"   => "https://github.com/ruby/rake/tree/v#{s.version}",
   }
 
-  s.files = %x[git ls-files -z].split("\x0").reject { |f| f.match(%r{^(test|spec|features|\.github)/}) } -
-            %w[.rubocop.yml .gitignore .travis.yml appveyor.yml]
+  s.files = [
+    "History.rdoc",
+    "MIT-LICENSE",
+    "README.rdoc",
+    "doc/command_line_usage.rdoc",
+    "doc/example/Rakefile1",
+    "doc/example/Rakefile2",
+    "doc/example/a.c",
+    "doc/example/b.c",
+    "doc/example/main.c",
+    "doc/glossary.rdoc",
+    "doc/jamis.rb",
+    "doc/proto_rake.rdoc",
+    "doc/rake.1",
+    "doc/rakefile.rdoc",
+    "doc/rational.rdoc",
+    "exe/rake",
+    "lib/rake.rb",
+    "lib/rake/application.rb",
+    "lib/rake/backtrace.rb",
+    "lib/rake/clean.rb",
+    "lib/rake/cloneable.rb",
+    "lib/rake/cpu_counter.rb",
+    "lib/rake/default_loader.rb",
+    "lib/rake/dsl_definition.rb",
+    "lib/rake/early_time.rb",
+    "lib/rake/ext/core.rb",
+    "lib/rake/ext/string.rb",
+    "lib/rake/file_creation_task.rb",
+    "lib/rake/file_list.rb",
+    "lib/rake/file_task.rb",
+    "lib/rake/file_utils.rb",
+    "lib/rake/file_utils_ext.rb",
+    "lib/rake/invocation_chain.rb",
+    "lib/rake/invocation_exception_mixin.rb",
+    "lib/rake/late_time.rb",
+    "lib/rake/linked_list.rb",
+    "lib/rake/loaders/makefile.rb",
+    "lib/rake/multi_task.rb",
+    "lib/rake/name_space.rb",
+    "lib/rake/packagetask.rb",
+    "lib/rake/phony.rb",
+    "lib/rake/private_reader.rb",
+    "lib/rake/promise.rb",
+    "lib/rake/pseudo_status.rb",
+    "lib/rake/rake_module.rb",
+    "lib/rake/rake_test_loader.rb",
+    "lib/rake/rule_recursion_overflow_error.rb",
+    "lib/rake/scope.rb",
+    "lib/rake/task.rb",
+    "lib/rake/task_argument_error.rb",
+    "lib/rake/task_arguments.rb",
+    "lib/rake/task_manager.rb",
+    "lib/rake/tasklib.rb",
+    "lib/rake/testtask.rb",
+    "lib/rake/thread_history_display.rb",
+    "lib/rake/thread_pool.rb",
+    "lib/rake/trace_output.rb",
+    "lib/rake/version.rb",
+    "lib/rake/win32.rb",
+    "rake.gemspec"
+  ]
   s.bindir = "exe"
   s.executables = s.files.grep(%r{^exe/}) { |f| File.basename(f) }
   s.require_paths = ["lib".freeze]