Is it possible to use build env to determine whether download source code in prepare stage or not

[zhoufenqin]

When I config a cnb image with blob url, like

apiVersion: kpack.io/v1alpha2
kind: Image
metadata:
  name: default.test
spec:
build:
  cache:
    volume:
      size: 1536Mi
  source:
    blob:
      url: https://xx.file.core.windows.net/bab958c1e4444a409bd8b20a8f12e039/xxx?se=2022-09-08T10%3A12%3A47Z&sp=r&sv=2021-06-08&sr=f&sig=xxx
......

Then the source code will be downloaded in the Prepare stage when a build pod is triggered. Sometimes, if I need to do some migration, like upgrade the buildpack version in the clusterstore, then use kpack-controller to trigger a new build pod automatically to generate a new image, then the Prepare stage may be failed because the blob.url SAS token is expired.

So if I use cache to store source code in /workspace layer, then how can I determine not to pull the source code again and again, just use the cached workspace layer generated in previous builds? It may helpful for some maintenance work, like helping a customer to generate a new image without CVE issues or upgrading the buildpack version. The expired blob.url may block this kind of operation.