@schema Source  { dir: string, branch: string, url: string }
@schema Build   { system: string, command: string, args: list<string> }
@schema Install { commands: list<string>, prefix: string }
@schema Hooks   { pre_build: string, post_install*: string }
@schema Package {
    id: string, name: string, type: string, version: string,
    source: Source, build: Build, install: Install, hooks: Hooks,
    build_deps: list<string>, run_deps: list<string>,
    updating_time: i32
}
