git commit broken ?

It seems that "git commit -a -c ORIG_HEAD" command do not work as
expected.

Here is an example:

	$ ls
	a b c

	$ git status
	nothing to commit

	$ echo "good modif" > a
	$ echo "temp modif" > c
	$ git-update-index a
	$ git commit -m "work in prog"

	$ git reset --soft HEAD^
	$ git status
	#
	# Updated but not checked in:
	#   (will commit)
	#
	#       modified: a
	#
	#
	# Changed but not updated:
	#   (use git-update-index to mark for commit)
	#
	#       modified: c
	#
	
	$ git commit -a -c ORIG_HEAD
	$ git status
	nothing to commit

So it seems that c has been commmited this time...Is it the expected
behaviour ?

My git version:

	$ git --version
	git version 1.3.0.rc3.g0ed4

Thanks
--
               Franck