Remove git-related files in unpacked gems

These files, including `.github` directory, are useless unless the
repository itself is contained as well.

Author: nobu

tool/lib/bundled_gem.rb

@@ -20,7 +20,10 @@ module BundledGem
 
   def unpack(file, *rest)
     pkg = Gem::Package.new(file)
-    prepare_test(pkg.spec, *rest) {|dir| pkg.extract_files(dir)}
+    prepare_test(pkg.spec, *rest) do |dir|
+      pkg.extract_files(dir)
+      FileUtils.rm_rf(Dir.glob(".git*", base: dir).map {|n| File.join(dir, n)})
+    end
     puts "Unpacked #{file}"
   rescue Gem::Package::FormatError, Errno::ENOENT
     puts "Try with hash version of bundled gems instead of #{file}. We don't use this gem with release version of Ruby."