Detached HEAD warning (again)

Hi all,

I strongly remember there being a discussion about this a few weeks ago, but I can't find it. Basically, someone wanted to introduce a warning every time someone commits on a detached HEAD. This was shot down because there already is a big warning when you detach your HEAD (with which I agree).

However, someone here: http://news.ycombinator.com/item?id=538619 pointed to an example here: http://book.git-scm.com/5_submodules.html , which works with submodules:

	$ git submodule update --init
	# sub/ is created
	$ (cd sub && touch a && git add a && git commit -am "Add new file")
	[detached HEAD 8641889] Add new file
	 0 files changed, 0 insertions(+), 0 deletions(-)
	 create mode 100644 a

	$ git submodule update
	$ ls sub/a
	ls: sub/a: No such file or directory

Now, it DOES say 'detached HEAD', but I still think this is something easily missed and something that can cause a lot of confusion. Perhaps a warning in such cases wouldn't hurt?

- Pieter