wicket git multiple workspaces

BRANCHES="master wicket-1.4.x wicket-1.5.x"
mkdir wicket
cd wicket

git clone https://git-wip-us.apache.org/repos/asf/wicket.git wicket-git-repo

for b in $BRANCHES; do
   mkdir $b
   pushd $b > /dev/null
   git init
   pushd .git > /dev/null
   for f in branches config hooks info objects refs packed-refs; do
      rm -rf $f
      ln -sf ../../wicket-git-repo/.git/$f $f
   done
   popd > /dev/null # out of the .git dir

   if [ `git branch | grep $b | wc -l` -eq 0 ]; then
      git branch --track $b origin/$b
   fi
   git checkout $b
   popd > /dev/null # out of the branch dir
done