Install packages defined by the import_line

Property definitions

nitc $ CommandInstall :: install_packages
	# Install packages defined by the `import_line`
	private fun install_packages(import_line: String)
	do
		var imports = import_line.parse_import
		for name, ext_package in imports do
			install_package(ext_package.id, ext_package.version)
		end
	end
src/nitpm.nit:93,2--100,4