Show help on error
Improve epilog formatting
Add new function DefaultAction
Refine
Add new field CLI.Desc
Improve multi-line usage formatting
Improve tests
Remove extension only on Windows
Improve tests
Refine
Add support for command
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Improve tests
Add support for subcommand
Update README.rst
Improve flag formatting
Change DefaultAction → Subcommand
Change ErrCmd → ErrCommand
Change FindCmd → FindCommand
Refine