Avoid repeated notifications (of available updates) when using Watchtower in "monitor only" mode

[truppelito]

Is your feature request related to a problem? Please describe.

If I update my containers automatically there may be issues during the update that I then only find out later. To avoid this, I update my containers manually. Nevertheless, I find it useful to know when updates are available. Therefore, I have Watchtower configured in "monitor only" mode and sending notifications to a Mattermost server. A scan is performed once per day.

My issue is as follows. Say one day Watchtower performs a scan and finds a container X with a new image version available with hash YYY. A notification is sent. Now let's say I'm on vacation for two weeks and unable to update the container. I will receive a notification every day until I do, which is annoying and unnecessary. One notification would suffice.

I may also not want to update a certain container, for whatever reason. Once again, receiving multiple notifications with the exact same information is unnecessary.

Describe the solution you'd like

My request: would it be possible for Watchtower to remember what notifications it has already sent (activated/deactivated by config argument, of course). That way, if a new image with hash YYY is available for container X, no matter how many scans are performed, only one notification is sent. Later a new-new image with hash ZZZ is available for X, send a notification again. But at least only one notification is sent per version.

Describe alternatives you've considered

Either accepting the notifications every day, or just rolling my own script to do what Watchtower does...

Additional context

No response

[github-actions]

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