kingpin

Enables declarative flag and command definition with chainable methods like 'Flag().Short().Bool()', reducing boilerplate and catching type errors at compile time, as shown in the simple example.

Automatically produces contextual help output with customizable Go templates, including compact and man page formats, making commands self-documenting without extra code.

Supports autocompletion for Bash, ZSH, and Fish out of the box, with APIs for dynamic hints, easing user interaction as detailed in the Shell Completion section.

Allows interspersed flags and file argument expansion via '@<file>' syntax, improving usability by letting flags appear anywhere after definition, as highlighted in the v2 changes.