Add configuration path discovery

identity.go

@@ -52,12 +52,22 @@ type Invocation struct {
 	reporter      *Reporter
 	enteredPath   string
 	canonicalPath string
+	renderHelp    func() Outcome
 }
 
 // Reporter returns the reporting facility supplied for this invocation. A
 // manually constructed Invocation has no reporter.
 func (inv Invocation) Reporter() *Reporter { return inv.reporter }
 
+// Help renders the selected command's help through this invocation's output.
+// It returns an operational failure when the invocation has no help renderer.
+func (inv Invocation) Help() Outcome {
+	if inv.renderHelp == nil {
+		return Failure("Command help is unavailable.")
+	}
+	return inv.renderHelp()
+}
+
 // EnteredPath returns the command path used to invoke the selected command,
 // excluding the executable name, flags, and operands. It is empty for an
 // Invocation that was not created by command execution.