shim: user switcher process management struct

This change moves all user switcher and shim management to the shim package and withholds output while shim is alive. This also eliminated all exit scenarios where revert is skipped.

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

main.go

@@ -53,15 +53,18 @@ func main() {
 	tryState()
 
 	// invoke app
-	r := 1
 	a, err := app.New(os)
 	if err != nil {
 		fmsg.Fatalf("cannot create app: %s\n", err)
 	} else if err = a.Seal(loadConfig()); err != nil {
-		logBaseError(err, "fortify: cannot seal app:")
+		logBaseError(err, "cannot seal app:")
 	} else if err = a.Start(); err != nil {
-		logBaseError(err, "fortify: cannot start app:")
-	} else if r, err = a.Wait(); err != nil {
+		logBaseError(err, "cannot start app:")
+	}
+
+	var r int
+	// wait must be called regardless of result of start
+	if r, err = a.Wait(); err != nil {
 		if r < 1 {
 			r = 1
 		}
@@ -70,5 +73,5 @@ func main() {
 	if err = a.WaitErr(); err != nil {
 		fmsg.Println("inner wait failed:", err)
 	}
-	os.Exit(r)
+	fmsg.Exit(r)
 }