Signing kinds are passed a single dependent job (from its kind dependency) to act on.
The transforms in
this common functionality. They expect a “signing description”, and produce a
task definition. The schema for a signing description is defined at the top of
signing.py, with copious comments.
In particular you define a set of upstream artifact urls (that point at the
dependent task) and can optionally provide a dependent name (defaults to build)
for use in
artifact-reference. You also need to provide
the signing formats to use.