[BUG] git add -u ignores --dry-run flag

Hi!

I think this is a bug in the built in implementation of git add -u

$ git --version
git version 1.5.5.1.373.ga3200
$ git init
Initialized empty Git repository in /home/hendeby/bar/.git/
$ echo foo > foo
$ git add foo && git commit -m "Test"
Created initial commit 7477e8b: Test
  1 files changed, 1 insertions(+), 0 deletions(-)
  create mode 100644 foo
$ echo foo >> foo
$ git add -u --dry-run
$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#       modified:   foo
#

I was expecting to get foo listed, and not actually added to the index.

I've had a quick look in builtin-add.c, and the -u option is tested for 
before the --dry-run option, and in the process of handling the -u 
option the code makes a jump that bypasses the --dry-run handling. 
Unfortunately, I'm not familiar enough with the code to see how to best 
fix it.

/Gustaf