Sample repro script for bundler issues

repro-1489.sh

#!/bin/bash

set -ex

mkdir -p /tmp/repro-1489
cd /tmp/repro-1489

bundle env
# Bundler 1.3.5
# Ruby 2.0.0 (2013-06-27 patchlevel 247) [x86_64-darwin12.4.0]
# Rubygems 2.0.3
# GEM_HOME
# Bundler settings
#   disable_local_branch_check
#     Set for the current user (/Users/xavier/.bundle/config): "true"

export GIT_DIR=bla
export GIT_WORK_TREE=bla

cat > Gemfile <<EOF
source "http://rubygems.org"
gem '', git: 'git://github.com/square/cane.git'
EOF

# Expected behaviour: should work
# Observed behaviour: git errors, fails
bundle install

Is there any workaround to fix this?