migrate backup actions to plugins

Signed-off-by: Steve Kriss <steve@heptio.com>

pkg/plugin/client_builder.go

@@ -0,0 +1,43 @@
+package plugin
+
+import (
+	"os/exec"
+
+	"github.com/hashicorp/go-hclog"
+	hcplugin "github.com/hashicorp/go-plugin"
+)
+
+type clientBuilder struct {
+	config *hcplugin.ClientConfig
+}
+
+func newClientBuilder(baseConfig *hcplugin.ClientConfig) *clientBuilder {
+	return &clientBuilder{
+		config: baseConfig,
+	}
+}
+
+func (b *clientBuilder) withPlugin(kind PluginKind, plugin hcplugin.Plugin) *clientBuilder {
+	if b.config.Plugins == nil {
+		b.config.Plugins = make(map[string]hcplugin.Plugin)
+	}
+	b.config.Plugins[string(kind)] = plugin
+
+	return b
+}
+
+func (b *clientBuilder) withLogger(logger hclog.Logger) *clientBuilder {
+	b.config.Logger = logger
+
+	return b
+}
+
+func (b *clientBuilder) withCommand(name string, args ...string) *clientBuilder {
+	b.config.Cmd = exec.Command(name, args...)
+
+	return b
+}
+
+func (b *clientBuilder) client() *hcplugin.Client {
+	return hcplugin.NewClient(b.config)
+}