Add example plugin for go-getter (kubernetes-sigs#923)

plugin/someteam.example.com/v1/gogetter/GoGetter

@@ -0,0 +1,44 @@
+#!/bin/bash
+# Copyright 2019 The Kubernetes Authors.
+# SPDX-License-Identifier: Apache-2.0
+
+# HashiCorp go-getter
+#
+# Reads a file like this
+#
+#  apiVersion: kustomize.config.k8s.io/v1
+#  kind: GoGetter
+#  metadata:
+#    name: external-dns
+#  url: github.com/kustless/external-dns.git  # (mandatory) URL to get
+#  overlay: base                              # (optional) relative path in the package
+#
+# download kustomize layes and build it to stdout
+#
+# Example execution:
+# ./plugin/someteam.example.com/v1/gogetter/GoGetter configFile.yaml
+
+set -e
+
+# YAML parsing function borrowed from ChartInflator
+function parseYaml {
+  local file=$1
+  while read -r line
+  do
+    local k=${line%:*}
+    local v=${line#*:}
+    local t=${v#"${v%%[![:space:]]*}"}  # trim leading space
+
+    if [ "$k" == "url" ]; then url=$t
+    elif [ "$k" == "overlay" ]; then overlay=$t
+    fi
+  done <"$file"
+}
+
+TMP_DIR=$(mktemp -d)
+
+parseYaml $1
+go-getter $url $TMP_DIR/got 2> /dev/null
+kustomize build $TMP_DIR/got/$overlay
+
+/bin/rm -rf $TMP_DIR

plugin/someteam.example.com/v1/gogetter/GoGetter_test.go

@@ -0,0 +1,45 @@
+// +build notravis
+
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+// Disabled on travis, because don't want to install go-getter on travis.
+
+package main_test
+
+import (
+	"testing"
+
+	kusttest_test "sigs.k8s.io/kustomize/v3/pkg/kusttest"
+	plugins_test "sigs.k8s.io/kustomize/v3/pkg/plugins/test"
+)
+
+// This test requires having the go-getter binary on the PATH.
+//
+func TestGoGetter(t *testing.T) {
+	tc := plugins_test.NewEnvForTest(t).Set()
+	defer tc.Reset()
+
+	tc.BuildExecPlugin(
+		"someteam.example.com", "v1", "GoGetter")
+
+	th := kusttest_test.NewKustTestPluginHarness(t, "/app")
+
+	m := th.LoadAndRunGenerator(`
+apiVersion: someteam.example.com/v1
+kind: GoGetter
+metadata:
+  name: example
+url: github.com/kustless/kustomize-examples.git
+`)
+
+	th.AssertActualEqualsExpected(m, `
+apiVersion: v1
+data:
+  altGreeting: Good Morning!
+  enableRisky: "false"
+kind: ConfigMap
+metadata:
+  name: the-map
+`)
+}