When diffing a submodule without any change, ask user to update submodule instead...
tree091cb0d009eb267b88e88db8934b962cfafe3c6a
-rw-r--r-- 367 .gitignore
-rw-r--r-- 543 .gitmodules
drwxr-xr-x - Languages
-rw-r--r-- 3400 build.txt
drwxr-xr-x - common
drwxr-xr-x - contrib
drwxr-xr-x - doc
drwxr-xr-x - ext
-rw-r--r-- 184 release.txt
drwxr-xr-x - src
drwxr-xr-x - test