To cite package ‘GetoptLong’ in publications use:

  Gu Z (2022). _GetoptLong: Parsing Command-Line Arguments and Simple
  Variable Interpolation_. R package version 1.1.0,
  <https://github.com/jokergoo/getoptlong>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {GetoptLong: Parsing Command-Line Arguments and Simple Variable Interpolation},
    author = {Zuguang Gu},
    year = {2022},
    note = {R package version 1.1.0},
    url = {https://github.com/jokergoo/getoptlong},
  }