Subcommands of Cargo frequently need to refer to a particular package within a dependency graph for various operations like updating, cleaning, building, etc. To solve this problem, Cargo supports Package ID Specifications. A specification is a string which is used to uniquely refer to one package within a graph of packages.
The formal grammar for a Package Id Specification is:
pkgid := pkgname | [ proto "://" ] hostname-and-path [ "#" ( pkgname | semver ) ] pkgname := name [ ":" semver ] proto := "http" | "git" | ...
Here, brackets indicate that the contents are optional.
These could all be references to a package
1.2.3 from the
The goal of this is to enable both succinct and exhaustive syntaxes for referring to packages in a dependency graph. Ambiguous references may refer to one or more packages. Most commands generate an error if more than one package could be referred to with the same specification.