Cannot reference non-HEAD or untagged commits

[mgoodness]

I believe #857 introduced a regression that prevents the use of specific GitHub commits as references unless they are either the HEAD of a branch or tagged. For example, building from the following kustomization.yaml succeeds because commit df7ed659a7b6280bb28838e0f87d54de435afe83 is tagged v0.1 in the repo.

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
  - https://github.com/mgoodness/sample-app-deploy/base?ref=df7ed659a7b6280bb28838e0f87d54de435afe83

However, commit 769f3aae20c1527e2ebc0fbbf89cc3a6e71e8d23 is neither a HEAD nor tagged, so the following build fails.

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
  - https://github.com/mgoodness/sample-app-deploy/base?ref=769f3aae20c1527e2ebc0fbbf89cc3a6e71e8d23

The root cause is that GitHub doesn't allow fetching commits by hash.

Using specific commits is considered by some a best practice, so we should find away to re-enable it.

[kinghajj]

This bug prevents us from updating past v2.0.3. Are there any plans to support this workflow again? We could work around this by pushing tags on the specific commits we reference, but that's not as secure, since Github won't let you prevent tags from being modified. Perhaps there could be two Cloner implementations, the post-#857 one and the pre-#857 one, and a command line flag used to enable the previous behavior?