Add SHA digest to check whether an upload is necessary

Sometimes the generated artifact has the same contents, e.g. when master branch changes but doesn't result in different output.

Start by locating the workflow or entry point that generates and uploads artifacts, then trace how it decides whether an upload is needed. Compare a generated artifact digest with the existing artifact and verify that unchanged contents skip the upload while changed contents still update it.

Written by the indexing model from the issue text.