Add capabilities to pull app spec from remote url

[renehernandez]

This would be a great extension to the current appfile capabilities. It would be nice if it could behave similar to what helm does with repos and pulling charts from remote.

Stable repo

Ideally, there would be a stable repo, that could host community-maintained app specifications. In addition, the implementation could support (at least having this in mind for the first iteration) adding custom repos, so that orgs could have their own private repos.

Note: Appfile would ship with the stable repo by default

Implementation

The appfile specification would need to be modified to support the new releases block instead of the old specs block

appfile spec overview

environments:
  review:
    - ..
  production:
    - ..

releases:
  - name: my-ghost # could be optional
    spec: stable/ghost
    values:
      - values.yaml
  ...

Repo commands

appfile repo add <http_url>

appfile repo list

appfile repo delete

appfile repo update

Limitations

• Spec published in the stable repo need to use a container image with public access. Of course the image field itself could be overwritten to point towards any internal/private container registry