I know that the GitHub web interface lets you search all repositories for files with a particular pathname (e.g. searching for path:/app/models/user.rb yields > 109k results), but is there a way to search all repositories for filenames independent of their subdirectory location? I tried using asterisks in the path argument, and that didn't seem to work.
Does the search user.rb in:path do what you want to do?
Alternatively there is also this search filename:user.rb