Strange library git glitch

I'm getting this strange output from 'git diff' bash$ git diff diff --git a/libraries/exceptions b/libraries/exceptions --- a/libraries/exceptions +++ b/libraries/exceptions @@ -1 +1 @@ -Subproject commit fe4166f8d23d8288ef2cbbf9e36118b6b99e0d7d +Subproject commit fe4166f8d23d8288ef2cbbf9e36118b6b99e0d7d-dirty No amount of git submodule update makes it go away. Any ideas? Thanks Simon