MakeProgressBar creates an appropriate progress.Meter for the environ in which it is called: - if MockMeter has been called, return that.

Null is a default NullMeter instance.

ANSIMeter is a progress.Meter that uses ANSI escape codes to make better use of the available horizontal space.

NullMeter is a Meter that does nothing.

QuietMeter is a Meter that _just_ shows Notify()s.

Meter is an interface to show progress to the user.