Add an optionalCompressionName helper

... and eliminate incorrectly named requiredCompression variables
by using it.

Should not change behavior.

Signed-off-by: Miloslav Trmač <[email protected]>

docker/docker_image_dest.go

@@ -27,6 +27,7 @@ import (
 	"github.com/containers/image/v5/internal/uploadreader"
 	"github.com/containers/image/v5/manifest"
 	"github.com/containers/image/v5/pkg/blobinfocache/none"
+	compressiontypes "github.com/containers/image/v5/pkg/compression/types"
 	"github.com/containers/image/v5/types"
 	"github.com/docker/distribution/registry/api/errcode"
 	v2 "github.com/docker/distribution/registry/api/v2"
@@ -311,6 +312,13 @@ func (d *dockerImageDestination) tryReusingExactBlob(ctx context.Context, info t
 	return false, private.ReusedBlob{}, nil
 }
 
+func optionalCompressionName(algo *compressiontypes.Algorithm) string {
+	if algo != nil {
+		return algo.Name()
+	}
+	return "nil"
+}
+
 // TryReusingBlobWithOptions checks whether the transport already contains, or can efficiently reuse, a blob, and if so, applies it to the current destination
 // (e.g. if the blob is a filesystem layer, this signifies that the changes it describes need to be applied again when composing a filesystem tree).
 // info.Digest must not be empty.
@@ -331,11 +339,7 @@ func (d *dockerImageDestination) TryReusingBlobWithOptions(ctx context.Context,
 			return true, reusedInfo, nil
 		}
 	} else {
-		requiredCompression := "nil"
-		if options.OriginalCompression != nil {
-			requiredCompression = options.OriginalCompression.Name()
-		}
-		logrus.Debugf("Ignoring exact blob match case due to compression mismatch ( %s vs %s )", options.RequiredCompression.Name(), requiredCompression)
+		logrus.Debugf("Ignoring exact blob match case due to compression mismatch ( %s vs %s )", options.RequiredCompression.Name(), optionalCompressionName(options.OriginalCompression))
 	}
 
 	// Then try reusing blobs from other locations.
@@ -356,14 +360,10 @@ func (d *dockerImageDestination) TryReusingBlobWithOptions(ctx context.Context,
 			}
 		}
 		if !impl.CandidateMatchesTryReusingBlobOptions(options, compressionAlgorithm) {
-			requiredCompression := "nil"
-			if compressionAlgorithm != nil {
-				requiredCompression = compressionAlgorithm.Name()
-			}
 			if !candidate.UnknownLocation {
-				logrus.Debugf("Ignoring candidate blob %s as reuse candidate due to compression mismatch ( %s vs %s ) in %s", candidate.Digest.String(), options.RequiredCompression.Name(), requiredCompression, candidateRepo.Name())
+				logrus.Debugf("Ignoring candidate blob %s as reuse candidate due to compression mismatch ( %s vs %s ) in %s", candidate.Digest.String(), options.RequiredCompression.Name(), optionalCompressionName(compressionAlgorithm), candidateRepo.Name())
 			} else {
-				logrus.Debugf("Ignoring candidate blob %s as reuse candidate due to compression mismatch ( %s vs %s ) with no location match, checking current repo", candidate.Digest.String(), options.RequiredCompression.Name(), requiredCompression)
+				logrus.Debugf("Ignoring candidate blob %s as reuse candidate due to compression mismatch ( %s vs %s ) with no location match, checking current repo", candidate.Digest.String(), options.RequiredCompression.Name(), optionalCompressionName(compressionAlgorithm))
 			}
 			continue
 		}