Merge pull request #1266 from cgwalters/copy-print-digest

copy: Add --digestfile

cmd/skopeo/copy.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"strings"
 
 	"github.com/containers/common/pkg/retry"
@@ -24,6 +25,7 @@ type copyOptions struct {
 	additionalTags    []string       // For docker-archive: destinations, in addition to the name:tag specified as destination, also add these
 	removeSignatures  bool           // Do not copy signatures from the source image
 	signByFingerprint string         // Sign the image using a GPG key with the specified fingerprint
+	digestFile        string         // Write digest to this file
 	format            optionalString // Force conversion of the image to a specified format
 	quiet             bool           // Suppress output information when copying images
 	all               bool           // Copy all of the images if the source is a list
@@ -66,6 +68,7 @@ See skopeo(1) section "IMAGE NAMES" for the expected format
 	flags.BoolVarP(&opts.all, "all", "a", false, "Copy all images if SOURCE-IMAGE is a list")
 	flags.BoolVar(&opts.removeSignatures, "remove-signatures", false, "Do not copy signatures from SOURCE-IMAGE")
 	flags.StringVar(&opts.signByFingerprint, "sign-by", "", "Sign the image using a GPG key with the specified `FINGERPRINT`")
+	flags.StringVar(&opts.digestFile, "digestfile", "", "Write the digest of the pushed image to the specified file")
 	flags.VarP(newOptionalStringValue(&opts.format), "format", "f", `MANIFEST TYPE (oci, v2s1, or v2s2) to use when saving image to directory using the 'dir:' transport (default is manifest type of source)`)
 	flags.StringSliceVar(&opts.encryptionKeys, "encryption-key", []string{}, "*Experimental* key with the encryption protocol to use needed to encrypt the image (e.g. jwe:/path/to/key.pem)")
 	flags.IntSliceVar(&opts.encryptLayer, "encrypt-layer", []int{}, "*Experimental* the 0-indexed layer indices, with support for negative indexing (e.g. 0 is the first layer, -1 is the last layer)")
@@ -175,7 +178,7 @@ func (opts *copyOptions) run(args []string, stdout io.Writer) error {
 	}
 
 	return retry.RetryIfNecessary(ctx, func() error {
-		_, err = copy.Image(ctx, policyContext, destRef, srcRef, &copy.Options{
+		manifestBytes, err := copy.Image(ctx, policyContext, destRef, srcRef, &copy.Options{
 			RemoveSignatures:      opts.removeSignatures,
 			SignBy:                opts.signByFingerprint,
 			ReportWriter:          stdout,
@@ -187,6 +190,18 @@ func (opts *copyOptions) run(args []string, stdout io.Writer) error {
 			OciEncryptLayers:      encLayers,
 			OciEncryptConfig:      encConfig,
 		})
-		return err
+		if err != nil {
+			return err
+		}
+		if opts.digestFile != "" {
+			manifestDigest, err := manifest.Digest(manifestBytes)
+			if err != nil {
+				return err
+			}
+			if err = ioutil.WriteFile(opts.digestFile, []byte(manifestDigest.String()), 0644); err != nil {
+				return fmt.Errorf("Failed to write digest to file %q: %w", opts.digestFile, err)
+			}
+		}
+		return nil
 	}, opts.retryOpts)
 }

docs/skopeo-copy.1.md

@@ -42,6 +42,10 @@ Path of the authentication file for the source registry. Uses path given by `--a
 
 Path of the authentication file for the destination registry. Uses path given by `--authfile`, if not provided.
 
+**--digestfile** _path_
+
+After copying the image, write the digest of the resulting image to the file.
+
 **--format, -f** _manifest-type_ Manifest type (oci, v2s1, or v2s2) to use when saving image to directory using the 'dir:' transport (default is manifest type of source)
 
 **--quiet, -q** suppress output information when copying images

integration/copy_test.go

@@ -246,6 +246,21 @@ func (s *CopySuite) TestCopyWithManifestListDigest(c *check.C) {
 	c.Assert(out, check.Equals, "")
 }
 
+func (s *CopySuite) TestCopyWithDigestfileOutput(c *check.C) {
+	tempdir, err := ioutil.TempDir("", "tempdir")
+	c.Assert(err, check.IsNil)
+	defer os.RemoveAll(tempdir)
+	dir1, err := ioutil.TempDir("", "copy-manifest-list-digest-dir")
+	c.Assert(err, check.IsNil)
+	defer os.RemoveAll(dir1)
+	digestOutPath := filepath.Join(tempdir, "digest.txt")
+	assertSkopeoSucceeds(c, "", "copy", "--digestfile="+digestOutPath, knownListImage, "dir:"+dir1)
+	readDigest, err := ioutil.ReadFile(digestOutPath)
+	c.Assert(err, check.IsNil)
+	_, err = digest.Parse(string(readDigest))
+	c.Assert(err, check.IsNil)
+}
+
 func (s *CopySuite) TestCopyWithManifestListStorageDigest(c *check.C) {
 	storage, err := ioutil.TempDir("", "copy-manifest-list-storage-digest")
 	c.Assert(err, check.IsNil)