Add a flag to control printing help before exiting

cli.go

@@ -36,11 +36,12 @@ name and description will be used to construct the help message for the app:
 func App(name, desc string) *Cli {
 	return &Cli{
 		Cmd: &Cmd{
-			name:          name,
-			desc:          desc,
-			optionsIdx:    map[string]*container.Container{},
-			argsIdx:       map[string]*container.Container{},
-			ErrorHandling: flag.ExitOnError,
+			name:            name,
+			desc:            desc,
+			optionsIdx:      map[string]*container.Container{},
+			argsIdx:         map[string]*container.Container{},
+			ErrorHandling:   flag.ExitOnError,
+			PrintHelpOnExit: true,
 		},
 	}
 }

commands.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -35,6 +36,8 @@ type Cmd struct {
 	// The command error handling strategy
 	ErrorHandling flag.ErrorHandling
 
+	PrintHelpOnExit bool
+
 	init    CmdInitializer
 	name    string
 	aliases []string
@@ -677,7 +680,9 @@ func (c *Cmd) parse(args []string, entry, inFlow, outFlow *flow.Step) error {
 
 	if err := c.fsm.Parse(args[:nargsLen]); err != nil {
 		fmt.Fprintf(stdErr, "Error: %s\n", err.Error())
-		c.PrintHelp()
+		if c.PrintHelpOnExit || errors.Is(err, fsm.ErrIncorrectUsage) {
+			c.PrintHelp()
+		}
 		c.onError(err)
 		return err
 	}

internal/fsm/fsm.go

@@ -1,15 +1,18 @@
 package fsm
 
 import (
+	"errors"
 	"sort"
 
-	"fmt"
-
 	"github.com/jawher/mow.cli/internal/container"
 	"github.com/jawher/mow.cli/internal/matcher"
 	"github.com/jawher/mow.cli/internal/values"
 )
 
+var (
+	ErrIncorrectUsage = errors.New("incorrect usage")
+)
+
 /*
 State is the basic building block in the FSM.
 A State can be final or not, and has transitions to other states
@@ -121,7 +124,7 @@ func (s *State) Parse(args []string) error {
 	pc := matcher.NewParseContext()
 	ok := s.apply(args, pc)
 	if !ok {
-		return fmt.Errorf("incorrect usage")
+		return ErrIncorrectUsage
 	}
 
 	if err := fillContainers(pc.Opts); err != nil {