[GitHub has a search system](https://github.com/search), [building on elastic search](http://www.elasticsearch.org/case-study/github/) that has [many advanced features](https://help.github.com/articles/searching-code) like searching for repositories or users. [Using Google, I can search GitHub for alternatives](https://www.google.de/search?q=site%3Agithub.com+Singleton+OR+Borg-Pattern). [The search syntax of GitHub however only covers negation operator](https://help.github.com/articles/search-syntax).

How do I use other logic operators in GitHub's search?

Is there perhaps a feature in elastic search that can be exploited for filtering or combining Boolean queries?