"git-meta log -p" appears inconsistent with "git meta diff"

The `-p` option to `git meta log` should list the changes to the files committed. However, instead it shows you the changes to the submodule SHAs, eg.
```
@@ -1 +1 @@
-Subproject commit ad227241dcd754d2cebf79ef5f170c5920383c0e
+Subproject commit e5232a12bf1c70f404ff91466b8751e491e7c7c4
```

To get the expected behavior I can add the flag `--submodule=diff`. However this is unexpected as the purpose of git meta is to pretend there is no submodules.