export changed files on git index to a temp folder, useful for a pre-hook that does linting

gistfile1.sh

tmpdir=`mktemp -d`
tree=`git write-tree`
git archive $tree \
    $(git diff --cached --name-status | 
         grep -v "^D" | 
         awk '{print $2}' 
     ) | 
    tar xv -C $tmpdir