class Rails::Generators::AppBase

def rails_version_specifier(gem_version = Rails.gem_version)
  if gem_version.segments.size == 3 || gem_version.release.segments.size == 3
    # ~> 1.2.3
    # ~> 1.2.3.pre4
    "~> #{gem_version}"
  else
    # ~> 1.2.3, >= 1.2.3.4
    # ~> 1.2.3, >= 1.2.3.4.pre5
    patch = gem_version.segments[0, 3].join(".")
    ["~> #{patch}", ">= #{gem_version}"]
  end
end