infinite loop with git branch -D and packed-refs

# this is with 1.4.4.2, spearce says master is also affected.
# (not subscribed, please Cc:)

mkdir test
cd test
git init-db
touch blah
git add blah
git commit -m "blah"
git checkout -b A
git checkout -b B
git checkout master
git pack-refs --all --prune
git branch -D A B # --> infinite loop in lockfile.c:remove_lock_file()