debian/watch: How to watch version tags and what to capture?

[<c.buhtz@posteo.jp>]

Hello together,

do I get it right that the syntax of the debain/watch file do use regex?

    https://repo .*/v?(\d.*)@ARCHIVE_EXT@

When an application do use version tages like "v1.4.0" and based on my
knowledge and experiments on regex101.com this won't work. Am I right?

There is also a capturing group in that example. What exactly should be
captured?

My proposal would be

    v+(\d.*)

but I'm not sure what the system expect or what part of the system do
use the watch file.

Background: The tracker didn't recognized the latest release of
backintime and I try to understand why and how to improve this myself.

https://sources.debian.org/src/backintime/1.3.3-4/debian/watch/

Thanks for your help.
Christian
Upstream maintenance team of Back In Time