As github pages does not support server side configuration (for example .htaccess files), it is impossible to get url rewriting to the index page working for a single page application.

Ideally, there should be a .gh-pages.yml or similar file in the repo root that has certain flags like

redirects:
    redirect_to: index.html
    try_files: true

The above would be the equivalent of the following for nginx

location / {
    root /path/to/site;
    index index.html;
    try_files $uri $uri/ /index.html =404;
}

The workaround is to use a hashbang like in angularjs html5 mode but this is fairly unsightly.

I think this feature is much wanted in the angular js community, and any other frontend javascript framework that supports the HTML5 History API.