title: Does yarn ignore .npmignore?
body: <p>I'm creating a npm package for self-learning purpose and published it on Github repo. The idea is that I want to install the package from one of the branch github repo rather.
  My folder contains:</p>
  
  <pre><code>a/
  b/
  c/
  .gitignore
  .npmignore
  package.json
  </code></pre>
  
  <p>I want to ignore certain file so I put them in <code>.npmignore</code>:</p>
  
  <pre><code>a
  c
  </code></pre>
  
  <p>When I <code>npm install git://github.com/USER/REPO.git#MY_AWESOME_BRANCH</code> and look into node_modules  </p>
  
  <pre><code>node_modules
  └── MY_PACKAGE_NAME
     ├── b/
     ├── .gitignore
     ├── .npmignore
     └── package.json
  </code></pre>
  
  <p>But when I <code>yarn add git://github.com/USER/REPO.git#MY_AWESOME_BRANCH</code> </p>
  
  <pre><code>node_modules
  └── MY_PACKAGE_NAME
     ├── a/
     ├── b/
     ├── c/
     ├── .gitignore
     ├── .npmignore
     └── package.json
  </code></pre>
  
  <p>Somehow, <code>yarn add</code> is ignoring <code>.npmignore</code> file. Is there a way to exclude certain files for both <code>npm install</code> and <code>yarn add</code> ?</p>