copy/single: add custom compressionFormat, compressionLevel fields

After containers#2048 there is no room for copy/multiple to pass custom compressionFormat to copySingleImage
while processing each instance, following PR introduces that functionality again and wraps options
to simpler struct.

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

copy/copy.go

@@ -251,8 +251,7 @@ func Image(ctx context.Context, policyContext *signature.PolicyContext, destRef,
 
 	if !multiImage {
 		// The simple case: just copy a single image.
-		singleImageOpts := copySingleImageOptions{requireCompressionFormatMatch: false}
-		single, err := c.copySingleImage(ctx, c.unparsedToplevel, nil, singleImageOpts)
+		single, err := c.copySingleImage(ctx, c.unparsedToplevel, nil, copySingleImageOptions{requireCompressionFormatMatch: false})
 		if err != nil {
 			return nil, err
 		}
@@ -274,8 +273,7 @@ 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)
-		singleImageOpts := copySingleImageOptions{requireCompressionFormatMatch: false}
-		single, err := c.copySingleImage(ctx, unparsedInstance, nil, singleImageOpts)
+		single, err := c.copySingleImage(ctx, unparsedInstance, nil, copySingleImageOptions{requireCompressionFormatMatch: false})
 		if err != nil {
 			return nil, fmt.Errorf("copying system image from manifest list: %w", err)
 		}

copy/multiple.go

@@ -128,8 +128,7 @@ 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)
-			singleImageOpts := copySingleImageOptions{requireCompressionFormatMatch: false}
-			updated, err := c.copySingleImage(ctx, unparsedInstance, &instanceCopyList[i].sourceDigest, singleImageOpts)
+			updated, err := c.copySingleImage(ctx, unparsedInstance, &instanceCopyList[i].sourceDigest, copySingleImageOptions{requireCompressionFormatMatch: false})
 			if err != nil {
 				return nil, fmt.Errorf("copying image %d/%d from manifest list: %w", i+1, len(instanceCopyList), err)
 			}

copy/single.go

@@ -42,6 +42,8 @@ type imageCopier struct {
 
 type copySingleImageOptions struct {
 	requireCompressionFormatMatch bool
+	compressionFormat             *compressiontypes.Algorithm // Compression algorithm to use, if the user explicitly requested one, or nil.
+	compressionLevel              *int
 }
 
 // copySingleImageResult carries data produced by copySingleImage
@@ -139,8 +141,8 @@ func (c *copier) copySingleImage(ctx context.Context, unparsedImage *image.Unpar
 	}
 	if c.options.DestinationCtx != nil {
 		// Note that compressionFormat and compressionLevel can be nil.
-		ic.compressionFormat = c.options.DestinationCtx.CompressionFormat
-		ic.compressionLevel = c.options.DestinationCtx.CompressionLevel
+		ic.compressionFormat = opts.compressionFormat
+		ic.compressionLevel = opts.compressionLevel
 	}
 	// Decide whether we can substitute blobs with semantic equivalents:
 	// - Don’t do that if we can’t modify the manifest at all