cmd/app: start application from configuration

This is currently not very usable due to hakurei immutable overlay mount limitations.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/app/main.go

@@ -6,8 +6,10 @@ package main
 
 import (
 	"context"
+	"errors"
 	"log"
 	"os"
+	"os/exec"
 	"os/signal"
 	"path/filepath"
 	"syscall"
@@ -124,7 +126,35 @@ func main() {
 		)
 	}
 
+	c.NewCommand(
+		"run", "Start the named application",
+		func(args []string) error {
+			if len(args) != 1 {
+				return errors.New("run requires 1 argument")
+			}
+
+			var config *hst.Config
+			f, err := os.Open(base.Append("app", args[0]).String())
+			if err != nil {
+				return err
+			}
+			config, err = parse(args[0], base, f)
+			if closeErr := f.Close(); err == nil {
+				err = closeErr
+			}
+			if err != nil {
+				return err
+			}
+
+			return run(ctx, msg, config)
+		},
+	)
+
 	c.MustParse(os.Args[1:], func(err error) {
+		if e, ok := errors.AsType[*exec.ExitError](err); ok && e != nil {
+			os.Exit(e.ExitCode())
+		}
+
 		if w, ok := err.(interface{ Unwrap() []error }); !ok {
 			log.Fatal(err)
 		} else {