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/web.go

@@ -34,42 +34,43 @@ import (
 // PIDFile could be set from build tag
 var PIDFile = "/run/gitea.pid"
 
-// CmdWeb represents the available web sub-command.
-var CmdWeb = &cli.Command{
-	Name:  "web",
-	Usage: "Start Gitea web server",
-	Description: `Gitea web server is the only thing you need to run,
+func newWebCommand() *cli.Command {
+	return &cli.Command{
+		Name:  "web",
+		Usage: "Start Gitea web server",
+		Description: `Gitea web server is the only thing you need to run,
 and it takes care of all the other things for you`,
-	Before: PrepareConsoleLoggerLevel(log.INFO),
-	Action: runWeb,
-	Flags: []cli.Flag{
-		&cli.StringFlag{
-			Name:    "port",
-			Aliases: []string{"p"},
-			Value:   "3000",
-			Usage:   "Temporary port number to prevent conflict",
+		Before: PrepareConsoleLoggerLevel(log.INFO),
+		Action: runWeb,
+		Flags: []cli.Flag{
+			&cli.StringFlag{
+				Name:    "port",
+				Aliases: []string{"p"},
+				Value:   "3000",
+				Usage:   "Temporary port number to prevent conflict",
+			},
+			&cli.StringFlag{
+				Name:  "install-port",
+				Value: "3000",
+				Usage: "Temporary port number to run the install page on to prevent conflict",
+			},
+			&cli.StringFlag{
+				Name:    "pid",
+				Aliases: []string{"P"},
+				Value:   PIDFile,
+				Usage:   "Custom pid file path",
+			},
+			&cli.BoolFlag{
+				Name:    "quiet",
+				Aliases: []string{"q"},
+				Usage:   "Only display Fatal logging errors until logging is set-up",
+			},
+			&cli.BoolFlag{
+				Name:  "verbose",
+				Usage: "Set initial logging to TRACE level until logging is properly set-up",
+			},
 		},
-		&cli.StringFlag{
-			Name:  "install-port",
-			Value: "3000",
-			Usage: "Temporary port number to run the install page on to prevent conflict",
-		},
-		&cli.StringFlag{
-			Name:    "pid",
-			Aliases: []string{"P"},
-			Value:   PIDFile,
-			Usage:   "Custom pid file path",
-		},
-		&cli.BoolFlag{
-			Name:    "quiet",
-			Aliases: []string{"q"},
-			Usage:   "Only display Fatal logging errors until logging is set-up",
-		},
-		&cli.BoolFlag{
-			Name:  "verbose",
-			Usage: "Set initial logging to TRACE level until logging is properly set-up",
-		},
-	},
+	}
 }
 
 func runHTTPRedirector() {