Rough out the beginnings of v1 config updates

Rough out simple image configuration edits, though apparently there's
more out there than just OCI v1.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

cmd/stevedore/config.go

@@ -1,28 +1,119 @@
 package main
 
 import (
-	"bytes"
+	"encoding/json"
+	"runtime"
+	"strings"
+	"time"
 
 	"github.com/Sirupsen/logrus"
-	"github.com/opencontainers/runtime-tools/generate"
+	"github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/urfave/cli"
 )
 
 var (
-	configFlags = []cli.Flag{}
+	configFlags = []cli.Flag{
+		cli.StringFlag{
+			Name:  "author",
+			Usage: "image author contact information",
+		},
+		cli.StringFlag{
+			Name:  "arch",
+			Usage: "image target architecture",
+		},
+		cli.StringFlag{
+			Name:  "os",
+			Usage: "image target operating system",
+		},
+		cli.StringFlag{
+			Name:  "user",
+			Usage: "user name to run containers as",
+		},
+		cli.StringSliceFlag{
+			Name:  "port",
+			Usage: "ports to expose when running containers",
+		},
+		cli.StringSliceFlag{
+			Name:  "env",
+			Usage: "environment variable to set when running containers",
+		},
+		cli.StringSliceFlag{
+			Name:  "entrypoint",
+			Usage: "container entry point",
+		},
+		cli.StringSliceFlag{
+			Name:  "cmd",
+			Usage: "container command",
+		},
+		cli.StringSliceFlag{
+			Name:  "volume",
+			Usage: "container volume",
+		},
+		cli.StringFlag{
+			Name:  "workingdir",
+			Usage: "container working directory",
+		},
+		cli.StringSliceFlag{
+			Name:  "label",
+			Usage: "container label",
+		},
+	}
 )
 
 func updateConfig(c *cli.Context, config []byte) []byte {
-	buffer := bytes.Buffer{}
-	g, err := generate.NewFromTemplate(bytes.NewReader(config))
+	image := v1.Image{}
+	if err := json.Unmarshal(config, &image); err != nil {
+		if len(config) > 0 {
+			logrus.Errorf("error importing image configuration, using original configuration")
+			return config
+		}
+	}
+	createdBytes, err := time.Now().MarshalText()
 	if err != nil {
-		logrus.Errorf("error importing template configuration, using original configuration")
+		logrus.Errorf("error setting image creation time: %v", err)
+	} else {
+		image.Created = string(createdBytes)
+	}
+	if image.Architecture == "" {
+		image.Architecture = runtime.GOARCH
+	}
+	if image.OS == "" {
+		image.OS = runtime.GOOS
+	}
+	if c.IsSet("author") {
+		image.Author = c.String("author")
+	}
+	if c.IsSet("arch") {
+		image.Architecture = c.String("arch")
+	}
+	if c.IsSet("os") {
+		image.OS = c.String("os")
+	}
+	if c.IsSet("env") {
+		for _, envSpec := range c.StringSlice("env") {
+			image.Config.Env = append(append([]string{}, image.Config.Env...), envSpec)
+		}
+	}
+	if c.IsSet("label") {
+		for _, labelSpec := range c.StringSlice("label") {
+			label := strings.SplitN(labelSpec, "=", 2)
+			if image.Config.Labels == nil {
+				image.Config.Labels = make(map[string]string)
+			}
+			if len(label) > 1 {
+				image.Config.Labels[label[0]] = label[1]
+			} else {
+				delete(image.Config.Labels, label[0])
+			}
+		}
+	}
+	if c.IsSet("workingdir") {
+		image.Config.WorkingDir = c.String("workingdir")
+	}
+	updatedImage, err := json.Marshal(&image)
+	if err != nil {
+		logrus.Errorf("error exporting updated image configuration, using original configuration")
 		return config
 	}
-	options := generate.ExportOptions{}
-	err = g.Save(buffer, options)
-	if err != nil {
-		logrus.Errorf("error exporting updated configuration, using original configuration")
-		return config
-	}
-	return buffer.Bytes()
+	return updatedImage
 }