bundle-server: use arg parser

Update 'main.go' to use the custom argument parser in the 'argparse'
package, specifying each command as a "subcommand" and invoking it with
'InvokeSubcommand()'.

By using the argument parser, the '-h' or '--help' flags will automatically
print usage information, and improperly formed invocations (invalid command,
no command specified, unused flags, etc.) will trigger an informative error
and exit with the usage string. This change substantially simplifies
'main.go' and improves user experience with the CLI.

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

cmd/git-bundle-server/main.go

@@ -21,17 +21,15 @@ func all() []argparse.Subcommand {
 func main() {
 	cmds := all()
 
-	if len(os.Args) < 2 {
-		log.Fatal("usage: git-bundle-server <command> [<options>]\n")
-		return
+	parser := argparse.NewArgParser("git-bundle-server <command> [<options>]")
+	parser.SetIsTopLevel(true)
+	for _, cmd := range cmds {
+		parser.Subcommand(cmd)
 	}
+	parser.Parse(os.Args[1:])
 
-	for i := 0; i < len(cmds); i++ {
-		if cmds[i].Name() == os.Args[1] {
-			err := cmds[i].Run(os.Args[2:])
-			if err != nil {
-				log.Fatal("Failed with error: ", err)
-			}
-		}
+	err := parser.InvokeSubcommand()
+	if err != nil {
+		log.Fatal("Failed with error: ", err)
 	}
 }