What steps did you take:
vendir sync with this config:

apiVersion: vendir.k14s.io/v1alpha1
kind: Config
minimumRequiredVersion: 0.12.0
directories:
- path: config/upstream
  contents:
  - path: serving
    git:
      url: https://github.com/knative/serving
      ref: v0.21.0
    includePaths:
    - config/core/**/*

What happened:
config/upstream/serving/config/core/300-imagecache.yaml is an invalid symlink, pointing to a file that doesn't exist.

What did you expect:
I'm not 100% sure, probably it should collapse the symlink into a regular file with the contents of the file it pointed to. Maybe this needs to be configurable.

Anything else you would like to add:
I looked into this a little and found it was broken in the library that vendir depends on: otiai10/copy#32

Environment:

• vendir version (execute vendir --version): 0.16.0
• OS (e.g. from /etc/os-release): ubuntu focal