I want the GitHub expression search

The GitHub search - especially the search box used for searching issues - is great. I love how it supports expressions for filtering and sorting:

is:issue is:open sort:created-asc

Something similar to this is also available on Gmail:

has:attachment in:unread

Is this a proprietary GitHub thing? or is there a Rails gem that I can grab to replicate the same behavior?

I found the absolutely great search_cop gem, which is similar, but I was wondering if what GitHub is using specifically is available to the public.

Anyone knows?