DefaultValues initiates a set of configs (Registerers) with their defaults.

DeprecatedFlag logs a warning when you try to use it.

IgnoredFlag ignores set value, without any warning.

NewDayValue makes a new DayValue; will round t down to the nearest midnight.

RegisterFlags registers flags with the provided Registerers.

DayValue is a model.Time that can be used as a flag.

URLValue is a url.URL that can be used as a flag.

Registerer is a thing that can RegisterFlags.

Strings is a list of strings.

StringSlice is a slice of strings that implements flag.Value.