.git bundled with package

What I Wanted to Do

Bundle package for publish and not include any .git files/directories

What Happened Instead

When running npm pack, a file .git/index is being included in the package contents. This problem does not seem to exist in npm 6.8 but exists in 6.9 and 6.9.1-next.0

npm i -g npm@6.8
npm pack
npm notice === Tarball Contents === 
npm notice 1.3kB   package.json                       
npm notice 621B    .eslintrc.js                       
npm notice 420B    avro_test.js                       
npm notice 161B    example_consumer_avro.js           
npm notice 406B    example_consumer_stream.js         
npm notice 151B    example_consumer.js                
npm notice 397B    example_producer.js                
npm notice 9.0kB   index.js                           
npm notice 109.4kB mihlfeld-npm_kafka_client-5.1.0.tgz
npm notice 532B    test_decoding.js                   
npm notice 312B    test_producer_buffer.js            
npm notice 147B    test/mocha_config.json             
npm notice 105B    test/output_location.js            
npm notice 2.7kB   test/test.js     


npm i -g npm@6.9
npm pack
npm notice === Tarball Contents === 
npm notice 1.3kB   package.json                       
npm notice 621B    .eslintrc.js                       
npm notice 420B    avro_test.js                       
npm notice 161B    example_consumer_avro.js           
npm notice 406B    example_consumer_stream.js         
npm notice 151B    example_consumer.js                
npm notice 397B    example_producer.js                
npm notice 9.0kB   index.js                           
npm notice 117.0kB mihlfeld-npm_kafka_client-5.1.0.tgz
npm notice 532B    test_decoding.js                   
npm notice 312B    test_producer_buffer.js            
npm notice 1.5kB   .git/index                         
npm notice 147B    test/mocha_config.json             
npm notice 105B    test/output_location.js            
npm notice 2.7kB   test/test.js       


Reproduction Steps

This is not an open source library, but rather hosted on an internal package manager.

.gitignore contents

node_modules
coverage
.nyc_output
test-output
out
test-results.xml
.vscode

Details

When running npm pack on 6.9 or newer, a file .git/index is bundled along with all the other files causing downstream issues

Platform Info

$ npm --versions
{ '@mihlfeld/npm_kafka_client': '5.1.0',
  npm: '6.9.0',
  ares: '1.15.0',
  brotli: '1.0.7',
  cldr: '35.1',
  http_parser: '2.8.0',
  icu: '64.2',
  modules: '64',
  napi: '4',
  nghttp2: '1.34.0',
  node: '10.16.0',
  openssl: '1.1.1b',
  tz: '2019a',
  unicode: '12.1',
  uv: '1.28.0',
  v8: '6.8.275.32-node.52',
  zlib: '1.2.11' }
$ node -p process.platform
linux

Pulled down latest npm-packlist (1.4.1) and wrote a code test checking this behavior and the test passed

  const gitIndexFile = path.join(pkg, ".git/index");
  fs.writeFileSync(gitIndexFile, "do not include me\n");