RFH: git show HEAD:$SUBMODULE

Hi,

at the moment, 'show HEAD:$SUBMODULE' fails horribly, as git-show abuses 
the revision walker to parse the command line parameters, and the revision 
walker does not like a non-existing commit.

Instead, it would be nicer to show the user something like

	HEAD:$SUBMODULE
	submodule at commit $COMMIT_NAME

However, I have no clue how to go about getting that.  I want to avoid 
having to parse the parameters twice, but I also do not want to fsck up 
the revision walker...

Ideas?

Ciao,
Dscho