Remove duplicated code in arg_package_spec.
Remove duplicated code in arg_package_spec.

nipunn1313/cargo,rust-lang/cargo,rustyhorde/cargo,rustyhorde/cargo,eminence/cargo,nipunn1313/cargo,eminence/cargo,eminence/cargo,rust-lang/cargo,rust-lang/cargo,eminence/cargo,rust-lang/cargo,rustyhorde/cargo,nipunn1313/cargo,rustyhorde/cargo,nipunn1313/cargo