At least I'd prefer a simple here-doc:

  tee -a .gitignore <<'EOF'
  output
  .psc*
  .purs*
  .spago
  EOF

(or use:

  cat <<'EOF' >> .gitignore
  output
  .psc*
  .purs*
  .spago
  EOF

But I think the tee-version more readily emphasize what's going on, and works with sudo).