copy: add support for ForceCompressionFormat

ForceCompressionFormat allows end users to force selected compression format
(set in DestinationCtx.CompressionFormat) which ensures that while copying
blobs of other compression algorithms are not reused.

Following flag is a frontend wrapper for: containers#2023
Will help in:
* containers/buildah#4613
* containers/podman#18660

Signed-off-by: Aditya R <arajan@redhat.com>

copy/copy.go

@@ -133,6 +133,10 @@ type Options struct {
 	// Invalid when copying a non-multi-architecture image. That will probably
 	// change in the future.
 	EnsureCompressionVariantsExist []OptionCompressionVariant
+	// ForceCompressionFormat ensures that the compression algorithm set in
+	// DestinationCtx.CompressionFormat is used exclusively, and blobs of other
+	// compression algorithms are not reused.
+	ForceCompressionFormat bool
 }
 
 // OptionCompressionVariant allows to supply information about
@@ -269,8 +273,11 @@ func Image(ctx context.Context, policyContext *signature.PolicyContext, destRef,
 		if len(options.EnsureCompressionVariantsExist) > 0 {
 			return nil, fmt.Errorf("EnsureCompressionVariantsExist is not implemented when not creating a multi-architecture image")
 		}
+		if (options.DestinationCtx == nil || options.DestinationCtx.CompressionFormat == nil) && options.ForceCompressionFormat {
+			return nil, fmt.Errorf("cannot use ForceCompressionFormat with undefined default compression format")
+		}
 		// The simple case: just copy a single image.
-		single, err := c.copySingleImage(ctx, c.unparsedToplevel, nil, copySingleImageOptions{requireCompressionFormatMatch: false})
+		single, err := c.copySingleImage(ctx, c.unparsedToplevel, nil, copySingleImageOptions{requireCompressionFormatMatch: c.options.ForceCompressionFormat})
 		if err != nil {
 			return nil, err
 		}
@@ -279,6 +286,9 @@ func Image(ctx context.Context, policyContext *signature.PolicyContext, destRef,
 		if len(options.EnsureCompressionVariantsExist) > 0 {
 			return nil, fmt.Errorf("EnsureCompressionVariantsExist is not implemented when not creating a multi-architecture image")
 		}
+		if (options.DestinationCtx == nil || options.DestinationCtx.CompressionFormat == nil) && options.ForceCompressionFormat {
+			return nil, fmt.Errorf("cannot use ForceCompressionFormat with undefined default compression format")
+		}
 		// This is a manifest list, and we weren't asked to copy multiple images.  Choose a single image that
 		// matches the current system to copy, and copy it.
 		mfest, manifestType, err := c.unparsedToplevel.Manifest(ctx)
@@ -295,7 +305,7 @@ func Image(ctx context.Context, policyContext *signature.PolicyContext, destRef,
 		}
 		logrus.Debugf("Source is a manifest list; copying (only) instance %s for current system", instanceDigest)
 		unparsedInstance := image.UnparsedInstance(rawSource, &instanceDigest)
-		single, err := c.copySingleImage(ctx, unparsedInstance, nil, copySingleImageOptions{requireCompressionFormatMatch: false})
+		single, err := c.copySingleImage(ctx, unparsedInstance, nil, copySingleImageOptions{requireCompressionFormatMatch: c.options.ForceCompressionFormat})
 		if err != nil {
 			return nil, fmt.Errorf("copying system image from manifest list: %w", err)
 		}

copy/multiple.go

@@ -29,8 +29,9 @@ const (
 )
 
 type instanceCopy struct {
-	op           instanceCopyKind
-	sourceDigest digest.Digest
+	op                     instanceCopyKind
+	sourceDigest           digest.Digest
+	forceCompressionFormat bool
 
 	// Fields which can be used by callers when operation
 	// is `instanceCopyClone`
@@ -122,9 +123,13 @@ func prepareInstanceCopies(list internalManifest.List, instanceDigests []digest.
 		if err != nil {
 			return res, fmt.Errorf("getting details for instance %s: %w", instanceDigest, err)
 		}
+		if (options.DestinationCtx == nil || options.DestinationCtx.CompressionFormat == nil) && options.ForceCompressionFormat {
+			return res, fmt.Errorf("cannot use ForceCompressionFormat with undefined default compression")
+		}
 		res = append(res, instanceCopy{
-			op:           instanceCopyCopy,
-			sourceDigest: instanceDigest,
+			op:                     instanceCopyCopy,
+			sourceDigest:           instanceDigest,
+			forceCompressionFormat: options.ForceCompressionFormat,
 		})
 		platform := platformV1ToPlatformComparable(instanceDetails.ReadOnly.Platform)
 		compressionList := compressionsByPlatform[platform]
@@ -230,7 +235,7 @@ func (c *copier) copyMultipleImages(ctx context.Context) (copiedManifest []byte,
 			logrus.Debugf("Copying instance %s (%d/%d)", instance.sourceDigest, i+1, len(instanceCopyList))
 			c.Printf("Copying image %s (%d/%d)\n", instance.sourceDigest, i+1, len(instanceCopyList))
 			unparsedInstance := image.UnparsedInstance(c.rawSource, &instanceCopyList[i].sourceDigest)
-			updated, err := c.copySingleImage(ctx, unparsedInstance, &instanceCopyList[i].sourceDigest, copySingleImageOptions{requireCompressionFormatMatch: false})
+			updated, err := c.copySingleImage(ctx, unparsedInstance, &instanceCopyList[i].sourceDigest, copySingleImageOptions{requireCompressionFormatMatch: instance.forceCompressionFormat})
 			if err != nil {
 				return nil, fmt.Errorf("copying image %d/%d from manifest list: %w", i+1, len(instanceCopyList), err)
 			}

copy/multiple_test.go

@@ -32,7 +32,7 @@ func TestPrepareCopyInstancesforInstanceCopyCopy(t *testing.T) {
 
 	for _, instance := range sourceInstances {
 		compare = append(compare, instanceCopy{op: instanceCopyCopy,
-			sourceDigest: instance})
+			sourceDigest: instance, forceCompressionFormat: false})
 	}
 	assert.Equal(t, instancesToCopy, compare)
 
@@ -42,6 +42,9 @@ func TestPrepareCopyInstancesforInstanceCopyCopy(t *testing.T) {
 	compare = []instanceCopy{{op: instanceCopyCopy,
 		sourceDigest: sourceInstances[1]}}
 	assert.Equal(t, instancesToCopy, compare)
+
+	_, err = prepareInstanceCopies(list, sourceInstances, &Options{Instances: []digest.Digest{sourceInstances[1]}, ImageListSelection: CopySpecificImages, ForceCompressionFormat: true})
+	require.EqualError(t, err, "cannot use ForceCompressionFormat with undefined default compression")
 }
 
 // Test `instanceCopyClone` cases.