Feature Request: Support Bazel renderer for Kubernetes YAML

[dbanetto]

Context

As a developer with a full bazel-ified monorepo (code and manifest generation together) it would have developer easier to have skaffold support rendering YAML from bazel directly.

Currently I work around this with by adding as many hooks to build the manifests as a I can to ensure they're up-to-date before the rawYaml renderer goes over them:

apiVersion: skaffold/v4beta13
kind: Config
metadata:
  name: k8s
build:
  tagPolicy:
    gitCommit:
      variant: CommitSha
  local:
    useDockerCLI: false
    useBuildkit: true
    concurrency: 0
  artifacts:
    - image: service
      bazel:
        target: //go/cmd/service:container-tarball.tar
        platforms:
          - platform: linux/amd64
            target: //build/platforms:linux_amd64
          - platform: linux/arm64
            target: //build/platforms:linux_arm64
      hooks:
        after:
          - command: ['bazel', 'build', '--remote_download_toplevel', '//manifests/local/service', '//manifests/local:local-namespaces-manifests']
            os: [darwin, linux]
manifests:
  rawYaml:
    - '../../../../build/bazel-out/darwin_arm64-fastbuild/bin/manifests/local/namespaces-manifests/*'
    - '../../../../build/bazel-out/darwin_arm64-fastbuild/bin/manifests/local/service/manifests/*'
deploy:
  kubectl:
    hooks:
      before:
        - host:
            command: ['bazel', 'build', '--remote_download_toplevel', '//manifests/local/service', '//manifests/local:local-namespaces-manifests']
            os: [darwin, linux]

However this is unstable with needing to manage the directory traversal & build options (darwin_arm64-fastbuild) so this config ends up not being portable between machines.

Feature Request

To support a renderer which takes a bazel target that outputs a directory (TreeArtifact) or a single YAML file then do the same processing as rawYaml over the file.

An example edit from the above config:

apiVersion: skaffold/v4beta13
kind: Config
metadata:
  name: k8s
build:
  tagPolicy:
    gitCommit:
      variant: CommitSha
  local:
    useDockerCLI: false
    useBuildkit: true
    concurrency: 0
  artifacts:
    - image: service
      bazel:
        target: //go/cmd/service:container-tarball.tar
        platforms:
          - platform: linux/amd64
            target: //build/platforms:linux_amd64
          - platform: linux/arm64
            target: //build/platforms:linux_arm64
manifests:
  bazel:
    targets:
      - '//manifests/local:local-namespaces-manifests'
      - '//manifests/local/service'
deploy:
  kubectl: {}

The //manifests/local:local-namespaces-manifests and //manifests/local/service targets are produced by rules_jsonnet's jsonnet_to_json as a single file & directory respectfully.