RealRunner is the default value of Runner and actually executes a command.

Run runs the given command and streams all the output to the given UI.

ShouldCleanup returns true for normal operation.

TestChrunner is a helper function that can be used to temporarily change the runner.

OttoSkipCleanupEnvVar, when set, tells Otto to avoid cleaning up its temporary workspace files, which can be helpful for debugging.

Runner is the function that is called to run a command.

MockRunner is a Runner implementation that records the calls.