fix: update check to follow .wh. specs

Author: parker-snyk

lib/extractor/index.ts

@@ -251,10 +251,20 @@ function layersWithLatestFileModifications(
 /**
  * check if a file is 'whited out', which is shown by
  * prefixing the filename with a .wh.
- * https://www.madebymikal.com/interpreting-whiteout-files-in-docker-image-layers/
+ * https://www.madebymikal.com/interpreting-whiteout-files-in-docker-image-layers
+ * https://github.com/opencontainers/image-spec/blob/main/layer.md#whiteouts
  */
 export function isWhitedOutFile(filename: string) {
-  return filename.includes(".wh.");
+  const lastSlashIndex = filename.lastIndexOf('/');
+  
+  if (lastSlashIndex === -1) {
+    // it's a file name, not a path
+    return filename.startsWith('.wh.');
+  } else {
+    // it's a path, so check the last part
+    const filenameToCheck = filename.substring(lastSlashIndex + 1);
+    return filenameToCheck.startsWith('.wh.');
+  }
 }
 
 function isBufferType(type: FileContent): type is Buffer {

test/lib/extractor/index.spec.ts

@@ -49,8 +49,10 @@ describe("isWhitedOutFile", () => {
 
   test("should handle .wh. at different positions", () => {
     expect(isWhitedOutFile(".wh.start")).toBe(true);
-    expect(isWhitedOutFile("middle.wh.file")).toBe(true);
-    expect(isWhitedOutFile("end.wh.")).toBe(true);
+    expect(isWhitedOutFile("middle.wh.file")).toBe(false);
+    expect(isWhitedOutFile("end.wh.")).toBe(false);
     expect(isWhitedOutFile("/deeply/nested/path/.wh.present")).toBe(true);
+    expect(isWhitedOutFile("/the/.wh./in/path/present")).toBe(false);
+
   });
 });