Make flag merging the default for new environments.

Previously it was necessary to set env.MergeFlags(true) to get the flag merging
behaviour. Change the default to be true instead. You can still disable merge
by setting env.MergeFlags(false).

command.go

@@ -55,10 +55,10 @@ type Env struct {
 	// is used as an [io.Writer]. If nil, it defaults to [os.Stderr].
 	Log io.Writer // where to write diagnostic output (nil for os.Stderr)
 
-	ctx    context.Context
-	cancel context.CancelCauseFunc
-	merge  bool
-	hflag  HelpFlags // default: no unlisted commands, no private flags
+	ctx       context.Context
+	cancel    context.CancelCauseFunc
+	skipMerge bool      // default: merge flags later in the argument list
+	hflag     HelpFlags // default: no unlisted commands, no private flags
 }
 
 // Context returns the context associated with e. If e does not have its own
@@ -101,7 +101,7 @@ func (e *Env) SetContext(ctx context.Context) *Env {
 //
 // Setting this option true modifies the flag parsing algorithm for commands
 // dispatched through e to "merge" flags matching the current command from the
-// remainder of the argument list. The default is false.
+// remainder of the argument list. The default is true.
 //
 // Merging allows flags for a command to be defined later in the command-line,
 // after subcommands and their own flags.  For example, given a command "one"
@@ -121,7 +121,7 @@ func (e *Env) SetContext(ctx context.Context) *Env {
 // unless the command's Init callback changes the setting.  Note that if a
 // subcommand defines a flag with the same name as its ancestor, the ancestor
 // will shadow the flag for the descendant.
-func (e *Env) MergeFlags(merge bool) *Env { e.merge = merge; return e }
+func (e *Env) MergeFlags(merge bool) *Env { e.skipMerge = !merge; return e }
 
 // HelpFlags sets the base help flags for e and returns e.
 //
@@ -161,7 +161,7 @@ func (e *Env) parseFlags(rawArgs []string) error {
 	e.Command.Flags.Usage = func() {}
 	e.Command.Flags.SetOutput(io.Discard)
 	toParse := rawArgs
-	if e.merge {
+	if !e.skipMerge {
 		flags, free, err := splitFlags(&e.Command.Flags, rawArgs)
 		if err != nil {
 			return err

example_test.go

@@ -40,7 +40,6 @@ This help text is printed by the "help" subcommand.`,
 			fs.StringVar(&opt.label, "label", "", "Label text")
 			fs.IntVar(&opt.private, "p", 0, "PRIVATE: Unadvertised flag")
 			fs.BoolVar(&opt.confirm, "y", false, "Confirm activity")
-			env.MergeFlags(true)
 		},
 
 		// Note that the "example" command does not have a Run function.

setup.sh

@@ -31,7 +31,7 @@ func main() {
          command.VersionCommand(),
       },
    }
-   command.RunOrFail(root.NewEnv(nil).MergeFlags(true), os.Args[1:])
+   command.RunOrFail(root.NewEnv(nil), os.Args[1:])
 }
 
 func runMain(env *command.Env) error {