Bash: Delete local branch before time

delete_local_branch

# Usage: delete_local_branch number_of_weeks_ago
# Eg: delete_local_branch 4

function delete_local_branch() {
  for k in $(git branch | sed /\*/d); do
    if [ -n "$(git log -1 --before='$1 week ago' -s $k)" -a "$k" != "develop" -a "$k" != "master" -a "$k" != "staging" ]; then
      echo "Delete $k"
      git branch -D $k
    fi
  done
}