Implemented checksum computation on image creation (necessary for new push primitive)

container.go

@@ -1,6 +1,7 @@
 package docker
 
 import (
+	"crypto/sha256"
 	"encoding/json"
 	"fmt"
 	"github.com/dotcloud/docker/rcli"
@@ -695,6 +696,18 @@ func (container *Container) ExportRw() (Archive, error) {
 	return Tar(container.rwPath(), Uncompressed)
 }
 
+func (container *Container) RwChecksum() (string, error) {
+	h := sha256.New()
+	rwData, err := container.ExportRw()
+	if err != nil {
+		return "", err
+	}
+	if _, err := io.Copy(h, rwData); err != nil {
+		return "", err
+	}
+	return string(h.Sum(nil)), nil
+}
+
 func (container *Container) Export() (Archive, error) {
 	if err := container.EnsureMounted(); err != nil {
 		return nil, err

graph.go

@@ -98,11 +98,13 @@ func (graph *Graph) Create(layerData Archive, container *Container, comment, aut
 		img.Parent = container.Image
 		img.Container = container.Id
 		img.ContainerConfig = *container.Config
-		if config == nil {
+		// FIXME: If an image is pulled from a raw URL (not created from a container),
-			if parentImage, err := graph.Get(container.Image); err == nil && parentImage != nil {
+		// its checksum will not be computed, which will cause a push to fail
-				img.Config = parentImage.Config
+		checksum, err := container.RwChecksum()
-			}
+		if err != nil {
+			return nil, err
 		}
+		img.Checksum = checksum
 	}
 	if err := graph.Register(layerData, img); err != nil {
 		return nil, err

image.go

@@ -18,6 +18,7 @@ import (
 type Image struct {
 	Id              string    `json:"id"`
 	Parent          string    `json:"parent,omitempty"`
+	Checksum        string    `json:"checksum,omitempty"`
 	Comment         string    `json:"comment,omitempty"`
 	Created         time.Time `json:"created"`
 	Container       string    `json:"container,omitempty"`