Detect builder repo and ref from oidc token

[asraa]

Signed-off-by: Asra Ali asraa@google.com

Fixes #24

[asraa]

Ready! @laurentsimon
Works at https://github.com/asraa/slsa-on-github-test/actions/runs/2072726014
much easier to just update the ref once!

[laurentsimon]

Thanks!

[asraa]

FYI doesn't want to issue for "Failed to get OIDC token from GitHub, response 403: Can't issue ID_TOKEN for audience 'https://github.com/slsa-framework/slsa-github-generator-go'."

might be because of the full qualification or a bad char... seemed like i had seen azure examples for this, will try to find docs about it

[asraa]

all good now -- i can't get fully qualified URI, and I suspect the 403 is because the context of the caller is not for the reusable workflow github repo :/

[laurentsimon]

all good now -- i can't get fully qualified URI, and I suspect the 403 is because the context of the caller is not for the reusable workflow github repo :/

Gotcha, that's probably good enough.