Ability to search Pull Requests

As far as I can tell, currently, you can only search for repositories. This is pretty useless since the number of repositories is usually pretty small.

On the other hand, I frequently want to search pull requests, either for a commit id, so I can see the pull request it is associated with, or for somthing in the description.

It would also be nice to be able to search branches in a repository, although that isn't as critical since I can use git commands to do that.