Add support for a filter cli flag in the sync command

[aslafy-z]

Allow filtering images to synchronize based on the name of the images.

eg: images.yaml

sources:
- repository: coreos/prometheus-operator
  host: quay.io
  tag: v0.40.0
- repository: super/secret
  tag: v0.3.0
  auth:
    username: DOCKER_USER_ENV
    password: DOCKER_PASSWORD_ENV
- repository: nginx
  digest: sha256:bbda10abb0b7dc57cfaab5d70ae55bd5aedfa3271686bace9818bba84cd22c29

sinker -m images.yaml push --filter nginx

will push only the images matching the filter (as a regexp).

[jpreese]

The image manifest is intended to be declarative in that whats defined in your manifest file, is what is pushed. Selectively pushing images in the manifest goes against that a little bit.

Would the imperative sinker push command work in this scenario?

sinker push -i image.com/repo:v1.0.0 -t host.com/repo

If not, what problem are you running into that you're wanting to be able to filter?