Add a Flags helper to construct SetFlags callbacks.

adapt_test.go

@@ -1,6 +1,7 @@
 package command_test
 
 import (
+	"flag"
 	"testing"
 
 	"github.com/creachadair/command"
@@ -75,3 +76,19 @@ func TestAdaptErrors(t *testing.T) {
 		})
 	}
 }
+
+func TestFlags(t *testing.T) {
+	var got int
+	c := &command.C{
+		SetFlags: command.Flags(func(fs *flag.FlagSet, v any) {
+			fs.IntVar(v.(*int), "test", 1, "Test flag")
+		}, &got),
+		Run: func(*command.Env) error { return nil },
+	}
+	if err := command.Run(c.NewEnv(nil), []string{"-test", "101", "ok"}); err != nil {
+		t.Fatalf("Run failed: %v", err)
+	}
+	if got != 101 {
+		t.Errorf("After Run: got %v, want 101", got)
+	}
+}

utils.go

@@ -7,6 +7,12 @@ import (
 	"strings"
 )
 
+// Flags returns a SetFlags function that calls bind(fs, v) with the flag set
+// and the given value v.
+func Flags(bind func(*flag.FlagSet, any), v any) func(*Env, *flag.FlagSet) {
+	return func(_ *Env, fs *flag.FlagSet) { bind(fs, v) }
+}
+
 // usageLines parses and normalizes usage lines. The command name is stripped
 // from the head of each line if it is present.
 func (c *C) usageLines() []string {