build() {
  ./talhelper completion bash > talhelper.bash
  ./talhelper completion fish > talhelper.fish
  ./talhelper completion zsh > _talhelper
}

package() {
  # bin
  install -Dm755 "./talhelper" "${pkgdir}/usr/bin/talhelper"
  # license
  install -Dm644 "./LICENSE" "${pkgdir}/usr/share/licenses/talhelper/LICENSE"
  # completions
  install -Dm644 talhelper.bash "${pkgdir}/usr/share/bash-completion/completions/talhelper"
  install -Dm644 talhelper.fish "${pkgdir}/usr/share/fish/completions/talhelper.fish"
  install -Dm644 _talhelper "${pkgdir}/usr/share/zsh/site-functions/_talhelper"
}

This will generate completions and throw them into the package for users!