"git pull" throws away dirty state

Ok, this is distressing, and I suspect it's another bug of mine due to 
unpack-trees changes, but before I delve into it deeper I thought I'd 
report it here and see if others see it too, and maybe it's due to 
something else..

I'm used to having dirty state in my tree, and still being able to do a 
lot of my normal work, very much including doing pulls from others. I 
expect that if the dirty state isn't relevant to the merge, it wil just 
remain, with a message like

	xyzzy: needs update
	Merge made by recursive.

and then after the merge my changes to xyzzy are still there.

That doesn't seem to work any more. The merge is successful, but it also 
updated the working tree, overwriting my dirty state!

Appended is a test-script for this behaviour, and I get:

	Before merge:
	diff --git a/a b/a
	index e965047..eacb93d 100644
	--- a/a
	+++ b/a
	@@ -1 +1,2 @@
	 Hello
	+Hi there
	a: needs update
	Merge made by recursive.
	 b |    1 +
	 1 files changed, 1 insertions(+), 0 deletions(-)
	After merge:

with the afte-merge diff being empty.

		Linus

---
#!/bin/sh

rm -rf test-repo
mkdir test-repo
cd test-repo

git init
echo Hello > a
echo Hi > b
git add a b
git commit -m "Initial commit"

git checkout -b newbranch
echo Hullo >> b
git commit -m "Change b in 'newbranch'" b

git checkout master
echo New file > c
git add c
git commit -m "Add new file"

echo Hi there >> a
echo Before merge:
git diff
git pull . newbranch
echo After merge:
git diff