[BUG] 'git merge --quiet' is not always quiet

In the following session, a 'git merge' command shows some output even
with the '--quiet' flag supplied.

    ~/tmp $ git init example
    Initialized empty Git repository in /tmp/example/.git/
    ~/tmp $ cd example/
    ~/tmp/example $ git commit --allow-empty -m'initial commit'
    [master (root-commit) a7329b5] initial commit
    ~/tmp/example $ git checkout -b b1
    Switched to a new branch 'b1'
    ~/tmp/example $ git commit --allow-empty -m'commit on branch'
    [b1 d15e5ac] commit on branch
    ~/tmp/example $ git checkout master
    Switched to branch 'master'
    ~/tmp/example $ git merge --quiet --no-ff --no-edit b1
    Already up-to-date!
    ~/tmp/example $

My expectation is that '--quiet' would suppress all output, even this one.

I'm on Git 1.9.1, but I've been informed on IRC that this happens even
on latest.

// Carl