Allow to copy layout from from OCI layout

src/main/java/land/oras/LayoutRef.java

@@ -84,6 +84,24 @@ public static LayoutRef parse(String name) {
         return new LayoutRef(path, tag);
     }
 
+    /**
+     * Return a new layout reference for a path
+     * @param path The path
+     * @return The layout ref
+     */
+    public LayoutRef forPath(Path path) {
+        return new LayoutRef(path, tag);
+    }
+
+    /**
+     * Return a new layout reference for a path
+     * @param ociLayout The OCI layout
+     * @return The layout ref
+     */
+    public LayoutRef forLayout(OCILayout ociLayout) {
+        return forPath(ociLayout.getPath());
+    }
+
     @Override
     public SupportedAlgorithm getAlgorithm() {
         // Default if not set

src/main/java/land/oras/OCI.java

@@ -404,7 +404,7 @@ public Manifest attachArtifact(T ref, ArtifactType artifactType, Annotations ann
                 .withSubject(subject);
         return pushManifest(
                 ref.withDigest(
-                        SupportedAlgorithm.SHA256.digest(manifest.toJson().getBytes(StandardCharsets.UTF_8))),
+                        SupportedAlgorithm.getDefault().digest(manifest.toJson().getBytes(StandardCharsets.UTF_8))),
                 manifest);
     }
 }

src/test/java/land/oras/LayoutRefTest.java

@@ -35,6 +35,12 @@ public class LayoutRefTest {
     @TempDir
     public static Path tempDir;
 
+    @TempDir
+    public static Path ociLayoutTempDir;
+
+    @TempDir
+    public static Path otherOciLayout;
+
     @Test
     void shouldParseLayoutWithAllParts() {
         String ociLayout = tempDir.resolve("foo").toString();
@@ -62,6 +68,14 @@ void shouldParseFolderNameOnly() {
         assertEquals("foo", layoutRef.getFolder().toString());
     }
 
+    @Test
+    void shouldReturnForOciLayout() {
+        OCILayout ociLayout = OCILayout.builder().defaults(ociLayoutTempDir).build();
+        LayoutRef layoutRef =
+                LayoutRef.parse(otherOciLayout.getFileName().toString()).forLayout(ociLayout);
+        assertEquals(layoutRef.getFolder(), ociLayoutTempDir, "Path should be the same");
+    }
+
     @Test
     void shouldFailWithInvalidRef() {
         assertThrows(OrasException.class, () -> LayoutRef.parse(""));