svoid test_nameRelativeToPhysicalSubdirectory() {
  File dir = createTempDir();
  File f = touchFile(newFile(dir, "hello"));
  File f2 = touchFile(newFile(dir, "sub/bla"));
  assertEqualsVerbose(null, nameRelativeToPhysicalSubdirectory(dir, dir));
  assertEqualsVerbose("hello", nameRelativeToPhysicalSubdirectory(f, dir));
  assertEqualsVerbose("sub" + fileSep() + "bla", nameRelativeToPhysicalSubdirectory(f2, dir));
}