Set the LocalName for the spec using a separate argument in the
NewSpec() constructor instead of reusing the `source` arg.
The name is already available in the calling scope in the client's
Resolve() method.
If the LocalName is an empty string, default to the remote (source)
reference. This is a change from the previous behaviour which only used
the base source.Name(). The full source corresponds to the
user-provided source value, which includes any specified tag or digest.
The `name` argument which is used in the `Resolve()` function should
always correspond to the user-provided container name.
Add the ListDigest to the container Spec struct and all its copies so we
can store list digests when they are available and pass them on to the
appropriate osbuild stages, sources, and inputs.
Copy the value whenever a spec is moved to a different representation.
Add a new `Resolve` method to `Client` that will resolve its `Target`
to the corresponding manifest digest id and its corresponding iamge
identifier. The former can be used in the URL to fetch a specific
image from the registry via `<name>@<digest>` and the latter uniquely
identifies a container image via the hash of its configuration object.
This should stay the same across pulls and is also the id returned via
`podman pull` and `podman images`.
Since (most) container images are OS and architecture specific a tag
often points to a manifest list that contains all available options.
Therefore the resolve operation needs to choose the correct arch for
image. A new pair of getters `Set{Architecture,Variant}Choice` lets
the user control which architecture/variant is selected during the
resolution process.
