from/import: record the base image's digest, if it has one

Record the digest of the base image's manifest, if there is a base
image.

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

Closes: #1724
Approved by: rhatdan

buildah.go

@@ -119,6 +119,9 @@ type Builder struct {
 	// FromImageID is the ID of the source image which was used to create
 	// the container, if one was used.  It should not be modified.
 	FromImageID string `json:"image-id"`
+	// FromImageDigest is the digest of the source image which was used to
+	// create the container, if one was used.  It should not be modified.
+	FromImageDigest string `json:"image-digest"`
 	// Config is the source image's configuration.  It should not be
 	// modified.
 	Config []byte `json:"config,omitempty"`
@@ -200,6 +203,7 @@ type BuilderInfo struct {
 	Type                  string
 	FromImage             string
 	FromImageID           string
+	FromImageDigest       string
 	Config                string
 	Manifest              string
 	Container             string
@@ -243,6 +247,7 @@ func GetBuildInfo(b *Builder) BuilderInfo {
 		Type:                  b.Type,
 		FromImage:             b.FromImage,
 		FromImageID:           b.FromImageID,
+		FromImageDigest:       b.FromImageDigest,
 		Config:                string(b.Config),
 		Manifest:              string(b.Manifest),
 		Container:             b.Container,

import.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/containers/buildah/docker"
 	"github.com/containers/buildah/util"
+	"github.com/containers/image/manifest"
 	is "github.com/containers/image/storage"
 	"github.com/containers/image/types"
 	"github.com/containers/storage"
@@ -47,6 +48,13 @@ func importBuilderDataFromImage(ctx context.Context, store storage.Store, system
 		}
 	}
 
+	imageDigest := ""
+	if manifestBytes, _, err := src.Manifest(ctx); err == nil {
+		if manifestDigest, err := manifest.Digest(manifestBytes); err == nil {
+			imageDigest = manifestDigest.String()
+		}
+	}
+
 	defaultNamespaceOptions, err := DefaultNamespaceOptions()
 	if err != nil {
 		return nil, err
@@ -57,6 +65,7 @@ func importBuilderDataFromImage(ctx context.Context, store storage.Store, system
 		Type:             containerType,
 		FromImage:        imageName,
 		FromImageID:      imageID,
+		FromImageDigest:  imageDigest,
 		Container:        containerName,
 		ContainerID:      containerID,
 		ImageAnnotations: map[string]string{},

new.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"github.com/containers/buildah/util"
+	"github.com/containers/image/manifest"
 	"github.com/containers/image/pkg/sysregistries"
 	is "github.com/containers/image/storage"
 	"github.com/containers/image/transports"
@@ -254,6 +255,7 @@ func newBuilder(ctx context.Context, store storage.Store, options BuilderOptions
 	}
 	image := options.FromImage
 	imageID := ""
+	imageDigest := ""
 	topLayer := ""
 	if img != nil {
 		image = getImageName(imageNamePrefix(image), img)
@@ -266,6 +268,11 @@ func newBuilder(ctx context.Context, store storage.Store, options BuilderOptions
 		if err != nil {
 			return nil, errors.Wrapf(err, "error instantiating image for %q", transports.ImageName(ref))
 		}
+		if manifestBytes, _, err := src.Manifest(ctx); err == nil {
+			if manifestDigest, err := manifest.Digest(manifestBytes); err == nil {
+				imageDigest = manifestDigest.String()
+			}
+		}
 		defer src.Close()
 	}
 
@@ -327,6 +334,7 @@ func newBuilder(ctx context.Context, store storage.Store, options BuilderOptions
 		Type:                  containerType,
 		FromImage:             image,
 		FromImageID:           imageID,
+		FromImageDigest:       imageDigest,
 		Container:             name,
 		ContainerID:           container.ID,
 		ImageAnnotations:      map[string]string{},