cli: parse and resolve flags

Copy all flags from upstream. The machinectl flag is dropped as it does nothing. the flag package is used to reduce complexity since we do not care about compatibility with upstream.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

cli.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+	"os/user"
+)
+
+var (
+	ego     *user.User
+	command []string
+	verbose bool
+	method  = machinectl
+
+	userName     string
+	methodFlags  [2]bool
+	printVersion bool
+)
+
+const (
+	machinectl uint8 = iota
+	machinectlBare
+	sudo
+)
+
+func init() {
+	flag.StringVar(&userName, "u", "ego", "Specify a username")
+	flag.BoolVar(&methodFlags[0], "sudo", false, "Use 'sudo' to change user")
+	flag.BoolVar(&methodFlags[1], "bare", false, "Use 'machinectl' but skip xdg-desktop-portal setup")
+	flag.BoolVar(&verbose, "v", false, "Verbose output")
+	flag.BoolVar(&printVersion, "V", false, "Print version")
+}
+
+func copyArgs() {
+	if printVersion {
+		fmt.Println(Version)
+		os.Exit(0)
+	}
+
+	command = flag.Args()
+
+	switch { // zero value is machinectl
+	case methodFlags[0]:
+		method = sudo
+	case methodFlags[1]:
+		method = machinectlBare
+	}
+
+	if u, err := user.Lookup(userName); err != nil {
+		if errors.As(err, new(user.UnknownUserError)) {
+			fmt.Println("unknown user", userName)
+		} else {
+			// unreachable
+			panic(err)
+		}
+
+		os.Exit(1)
+	} else {
+		ego = u
+	}
+
+	if verbose {
+		fmt.Println("Running command", command, "as user", ego.Username, "("+ego.Uid+")")
+	}
+}