When adding packages using Pkg one can choose version using @x.y.z syntax after the package name. Is this number tied to the version entry in the project.toml file? Is this unrelated to any versioning in git (ie tag?).
Is it then possible to choose a specific version when loading from an unregistered repository (will Pkg somehow search all commits until it finds a project.toml with matching version) or must one then use the #commit-sha/branch syntax?
When we use the @x.y.z syntax, is this related to individual registrations in a package registry?
The vagueness of the questions reflects my confusion. Enlightenment appreciated.
“the version” of a package is the entry from the Project.toml at the time of registration in some registry, i.e. if my Project.toml contains version: 0.2.1-rc1 then pkg> add MyPackage@0.2.1-rc1 will look in the registry for the specific code that was registered under this number. If nobody ever registered a version with this number, then the package manager won’t be able to install it
a registry can contain many versions of the same package, of course, but one version is always a unique snapshot so to say
a package that is not registered can have a “version” (the entry in the Project.toml), which will also be displayed if you list the packages with pkg> status, but it’s just a “volatile” label for the current code; you cannot ask for a specific version of a package without a registry – this is what keeps track of all the past versions that have been registered
git tags and branches (or commit IDs) can also be used similarly to version numbers, just with # instead of @ after the package name (or URL), as described in the link above
So in short, I think the answers to your questions are “yes, yes, (no, yes), yes” Hope that helps clear up some confusion.
The @ syntax is related to registry information only. The # syntax is related to git commits/branches/tags only. In neither case Pkg examines Project.toml.
Hope that helps clear up some confusion.