Make kpromo pr staging repo prefix configurable #1512
Description
What would you like to be added:
A new command line flag for kpromo pr should be added to make the staging repo prefix configurable.
Why is this needed:
SIG K8s-Infra is now suggesting new projects to create their staging repos at us-central1-docker.pkg.dev/k8s-staging-images/<project> instead of the gcr.io/k8s-staging-<project> form kpromo assumes. kubernetes/k8s.io#7703 (comment)
e.g. Running kpromo pr for the dra-example-driver project runs into the error:
could not find Manifest for "gcr.io/k8s-staging-dra-example-driver"
because its staging repo is at us-central1-docker.pkg.dev/k8s-staging-images/dra-example-driver:
https://github.com/kubernetes/k8s.io/blob/e41113e88b5b85554d0c1b2ce33b878627e49813/registry.k8s.io/manifests/k8s-staging-dra-example-driver/promoter-manifest.yaml#L3