Issue #475 Add flag for image compress layer for oci destination

Signed-off-by: Praveen Kumar <kumarpraveen.nitdgp@gmail.com>

.gitignore

@@ -7,3 +7,6 @@ tools.timestamp
 
 # Visual Studio Code
 .vscode/*
+
+# trash
+trash.lock

oci/layout/oci_dest.go

@@ -18,9 +18,10 @@ import (
 )
 
 type ociImageDestination struct {
-	ref           ociReference
-	index         imgspecv1.Index
-	sharedBlobDir string
+	ref                      ociReference
+	index                    imgspecv1.Index
+	sharedBlobDir            string
+	acceptUncompressedLayers bool
 }
 
 // newImageDestination returns an ImageDestination for writing to an existing directory.
@@ -43,6 +44,7 @@ func newImageDestination(sys *types.SystemContext, ref ociReference) (types.Imag
 	d := &ociImageDestination{ref: ref, index: *index}
 	if sys != nil {
 		d.sharedBlobDir = sys.OCISharedBlobDirPath
+		d.acceptUncompressedLayers = sys.OCIAcceptUncompressedLayers
 	}
 
 	if err := ensureDirectoryExists(d.ref.dir); err != nil {
@@ -81,6 +83,9 @@ func (d *ociImageDestination) SupportsSignatures(ctx context.Context) error {
 }
 
 func (d *ociImageDestination) DesiredLayerCompression() types.LayerCompression {
+	if d.acceptUncompressedLayers {
+		return types.PreserveOriginal
+	}
 	return types.Compress
 }
 

types/types.go

@@ -364,6 +364,8 @@ type SystemContext struct {
 	OCIInsecureSkipTLSVerify bool
 	// If not "", use a shared directory for storing blobs rather than within OCI layouts
 	OCISharedBlobDirPath string
+	// Allow UnCompress image layer for OCI image layer
+	OCIAcceptUncompressedLayers bool
 
 	// === docker.Transport overrides ===
 	// If not "", a directory containing a CA certificate (ending with ".crt"),