view: add peek flag and propagate

Add a peek flag -p to the view commands to open the message viewer
without setting the "seen" flag. If the flag is set, it would ignore the
"auto-mark-read" config.

The SetSeen flag will be propagated in case the message viewer moves on
to other messages, i.e. with the delete or archive commands.

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

commands/msgview/next.go

@@ -42,7 +42,7 @@ func (NextPrevMsg) Execute(aerc *widgets.Aerc, args []string) error {
 		aerc.RemoveTab(mv)
 		return nil
 	}
-	lib.NewMessageStoreView(nextMsg, acct.UiConfig().AutoMarkRead,
+	lib.NewMessageStoreView(nextMsg, mv.MessageView().SeenFlagSet(),
 		store, aerc.Crypto, aerc.DecryptKeys,
 		func(view lib.MessageView, err error) {
 			if err != nil {