Merge branch 'ls/p4-tmp-refs'

"git p4" used a location outside $GIT_DIR/refs/ to place its
temporary branches, which has been moved to refs/git-p4-tmp/.

* ls/p4-tmp-refs:
git-p4: place temporary refs used for branch import under refs/git-p4-tmp

diff --cc git-p4.py
Simple merge