Switch cmd/ to use constructor functions. (#36962)

This is a step towards potentially splitting command groups into their
own folders to clean up `cmd/` as one folder for all cli commands.
Returning fresh command instances will also aid in adding tests as you
don't need to concern yourself with the whole command tree being one
mutable variable.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

cmd/generate.go

@@ -15,45 +15,52 @@ import (
 	"github.com/urfave/cli/v3"
 )
 
-var (
-	// CmdGenerate represents the available generate sub-command.
-	CmdGenerate = &cli.Command{
+func newGenerateCommand() *cli.Command {
+	return &cli.Command{
 		Name:  "generate",
 		Usage: "Generate Gitea's secrets/keys/tokens",
 		Commands: []*cli.Command{
-			subcmdSecret,
+			newGenerateSecretCommand(),
 		},
 	}
+}
 
-	subcmdSecret = &cli.Command{
+func newGenerateSecretCommand() *cli.Command {
+	return &cli.Command{
 		Name:  "secret",
 		Usage: "Generate a secret token",
 		Commands: []*cli.Command{
-			microcmdGenerateInternalToken,
-			microcmdGenerateLfsJwtSecret,
-			microcmdGenerateSecretKey,
+			newGenerateInternalTokenCommand(),
+			newGenerateLfsJWTSecretCommand(),
+			newGenerateSecretKeyCommand(),
 		},
 	}
+}
 
-	microcmdGenerateInternalToken = &cli.Command{
+func newGenerateInternalTokenCommand() *cli.Command {
+	return &cli.Command{
 		Name:   "INTERNAL_TOKEN",
 		Usage:  "Generate a new INTERNAL_TOKEN",
 		Action: runGenerateInternalToken,
 	}
+}
 
-	microcmdGenerateLfsJwtSecret = &cli.Command{
+func newGenerateLfsJWTSecretCommand() *cli.Command {
+	return &cli.Command{
 		Name:    "JWT_SECRET",
 		Aliases: []string{"LFS_JWT_SECRET"},
 		Usage:   "Generate a new JWT_SECRET",
 		Action:  runGenerateLfsJwtSecret,
 	}
+}
 
-	microcmdGenerateSecretKey = &cli.Command{
+func newGenerateSecretKeyCommand() *cli.Command {
+	return &cli.Command{
 		Name:   "SECRET_KEY",
 		Usage:  "Generate a new SECRET_KEY",
 		Action: runGenerateSecretKey,
 	}
-)
+}
 
 func runGenerateInternalToken(_ context.Context, c *cli.Command) error {
 	internalToken, err := generate.NewInternalToken()