GitHub will already generate a .gitignore file when you create a repository on its website. It would be nice if the .gitignore file was based on the type of project being created.

Right, but how does it know that? There is no "Create Ruby on Rails project" command in git. How will it know what to include? Will it have to scan and somehow detect that it's an RoR project? And check the version of it?

Much simpler to leave this stuff to a RoR-specific tool. Maybe the .gitignore should be a default file when creating an RoR project.