CommandLineErrorf is like fmt.Errorf except that it returns a value that triggers printing of the command line help.

Main should be invoked directly by main function.

Run is the inner loop for Main; invoked by Main, recursively by Run, and by various tests.

Profile can be embedded in your application struct to automatically add command line arguments and handling for the common profiling methods.

Application is the interface that must be satisfied by an object passed to Main.