NewApp creates an app with sane defaults.

AppHelpTemplate is the test template for the default, global app help topic.

ClefAppHelpTemplate is the template for the default, global app help topic.

DirectoryFlag is custom cli.Flag type which expand the received string to an absolute path.

FlagGroup is a collection of flags belonging to a single topic.

HelpData is a one shot struct to pass to the usage template.

byCategory sorts an array of FlagGroup by Name in the order defined in AppHelpFlagGroups.

DirectoryString is custom type which is registered in the flags library which cli uses for argument parsing.