Support standalone mode for framework functions

kyaml/fn/framework/example2/Dockerfile

@@ -0,0 +1,12 @@
+# Copyright 2019 The Kubernetes Authors.
+# SPDX-License-Identifier: Apache-2.0
+
+FROM golang:1.13-stretch
+ENV CGO_ENABLED=0
+WORKDIR /go/src/
+COPY . .
+RUN go build -v -o /usr/local/bin/function ./
+
+FROM alpine:latest
+COPY --from=0 /usr/local/bin/function /usr/local/bin/function
+CMD ["function"]

kyaml/fn/framework/example2/config.yaml

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+# Copyright 2019 The Kubernetes Authors.
+# SPDX-License-Identifier: Apache-2.0
+
+apiVersion: example.com/v1alpha1
+kind: Example
+key: key
+value: value

kyaml/fn/framework/example2/main.go

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+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"text/template"
+
+	"sigs.k8s.io/kustomize/kyaml/fn/framework"
+)
+
+func main() {
+	type api struct {
+		Key   string `json:"key" yaml:"key"`
+		Value string `json:"value" yaml:"value"`
+	}
+	cmd := framework.TemplateCommand{
+		API: &api{},
+		Template: template.Must(template.New("example").Parse(`
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: foo
+  namespace: default
+  annotations:
+    {{ .Key }}: {{ .Value }}
+`)),
+	}.GetCommand()
+	if err := cmd.Execute(); err != nil {
+		fmt.Fprintln(cmd.OutOrStderr(), err)
+		os.Exit(1)
+	}
+}