Fork imapsql-ctl utility from go-imap-sql repo

1. There is only one version for maddy and imapsql-ctl utility.
This prevents confusion about compatibility.

2. Modified imapsql-ctl understands maddy config format, this allows
it to read needed values from it without the need for lengthy commmand
line arguments.

Closes #148.

cmd/imapsql-ctl/flags.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/urfave/cli"
+)
+
+func msgsFlags(ctx *cli.Context) error {
+	if err := connectToDB(ctx); err != nil {
+		return err
+	}
+
+	if !ctx.GlobalBool("unsafe") {
+		return errors.New("Error: Refusing to edit mailboxes without --unsafe")
+	}
+
+	username := ctx.Args().First()
+	if username == "" {
+		return errors.New("Error: USERNAME is required")
+	}
+	name := ctx.Args().Get(1)
+	if name == "" {
+		return errors.New("Error: MAILBOX is required")
+	}
+	seqStr := ctx.Args().Get(2)
+	if seqStr == "" {
+		return errors.New("Error: SEQ is required")
+	}
+
+	seq, err := imap.ParseSeqSet(seqStr)
+	if err != nil {
+		return err
+	}
+
+	u, err := backend.GetUser(username)
+	if err != nil {
+		return err
+	}
+
+	mbox, err := u.GetMailbox(name)
+	if err != nil {
+		return err
+	}
+
+	flags := ctx.Args()[3:]
+	if len(flags) == 0 {
+		return errors.New("Error: at least once FLAG is required")
+	}
+
+	var op imap.FlagsOp
+	switch ctx.Command.Name {
+	case "add-flags":
+		op = imap.AddFlags
+	case "rem-flags":
+		op = imap.RemoveFlags
+	case "set-flags":
+		op = imap.SetFlags
+	default:
+		panic("unknown command: " + ctx.Command.Name)
+	}
+
+	return mbox.UpdateMessagesFlags(ctx.IsSet("uid"), seq, op, flags)
+}