Rake task to generate an html branch for jekyll

jekyll_generate.rb

desc "Commit website to html branch"
task :html do
  system <<-GITFOO
    test -e 'for_html' && rm -rf for_html
    test -e '.git/html.index' && rm .git/html.index

    jekyll --no-auto for_html
    export GIT_INDEX_FILE=.git/html.index
    git add -f for_html
    tree_id=$(git write-tree --prefix=for_html/)
    new_commit=$(echo "New website!"|git commit-tree $tree_id -p refs/heads/html)
    git update-ref refs/heads/html $new_commit

    test -e 'for_html' && rm -rf for_html
    test -e '.git/html.index' && rm .git/html.index
  GITFOO
end