[BUG] fatal error during merge

It took a while to make a minimal test case for this, but I think that all
the below steps are required. It ends up with this message:

after/one: unmerged (e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)
fatal: git write-tree failed to write a tree

and the file that was moved has disappeared from the working tree.

I have tested the script with Git 1.6.0.2, but the real scenario that made
this appear seems to also fail with master and next from git.git.

Cheers,
Anders.


Test script:

mkdir am-merge-fail
cd am-merge-fail
git init

mkdir before
touch before/one after
git add -A
git commit -minitial

rm -f after
git mv before after
git commit -mmove

git checkout -b parallel HEAD~
touch another
git add -A
git commit -mparallel

git merge master