Does self have a README.md file?

Property definitions

nitc $ MPackage :: has_readme
	# Does `self` have a README.md file?
	fun has_readme: Bool do
		var readme_path = self.readme_path
		if readme_path == null then return false
		return readme_path.file_exists
	end
src/model/mpackage.nit:107,2--112,4