message: gltfpack: Introduce test mode
  In test mode, we load and process all files specified after -test
  command line argument, but we don't save them.
  This is very convenient for doing batch performance and validity testing
  using xargs.
diff: @@ -3272,6 +3272,11 @@ int pack(const char* input, const char* output, const Settings& settings)
  cgltf_free(data);
  + if (!output)
  + {
  + return 0;
  + }
  +
  const char* oext = strrchr(output, '.');
  if (oext && (strcmp(oext, ".gltf") == 0 || strcmp(oext, ".GLTF") == 0))
  @@ -3356,6 +3361,7 @@ int main(int argc, char** argv)
  const char* input = 0;
  const char* output = 0;
  bool help = false;
  + int test = 0;
  for (int i = 1; i < argc; ++i)
  {
  @@ -3413,6 +3419,11 @@ int main(int argc, char** argv)
  {
  help = true;
  }
  + else if (strcmp(arg, "-test") == 0)
  + {
  + test = i + 1;
  + break;
  + }
  else
  {
  fprintf(stderr, "Unrecognized option %s\n", arg);
  @@ -3420,6 +3431,14 @@ int main(int argc, char** argv)
  }
  }
  + if (test)
  + {
  + for (int i = test; i < argc; ++i)
  + pack(argv[i], NULL, settings);
  +
  + return 0;
  + }
  +
  if (!input || !output || help)
  {
  fprintf(stderr, "Usage: gltfpack [options] -i input -o output\n");
  