Adding only dist folder to the gh-pages/master branch

I am using organisation guthub-pages to host a static website which I am developing using ember.

My website output branch is master. I am keeping the ember specific code in ember branch as specified in the readme.

According to me, executing ember github-pages:commit --message "abc" --branch master command should do the following:

1. Build the ember project.
2. Copy the dist folder from ember branch to master branch.

But contrary to that it is actually copying everything from ember branch to master branch.

Is this the expected behavior? Or am I missing something? Is there any way to make it copy only the dist folder to the master branch?

My friend originally asked the question here, but as there is no response I thought of going to SO community.