Feature: Exclude existing alerts in group notification

What did you do?
Let's say you got 2 firing alerts in a single group in alertmanager.

[firing]
alertname=ServerOff
server=EUW1
[firing]
alertname=ServerOff
server=EUW2

If now one alert is resolved or added, the alertmanager creates a notification about this change but the notification includes all existing alerts of that group and not only the alerts with state changes.

Perhaps i missed a config value which enables this feature already(?) 🤔

What did you expect to see?
Expected notification content:

[resolved]
alertname=ServerOff
server=EUW2

What did you see instead? Under which circumstances?
Actual notification content when EUW2 gets resolved:

[firing]
alertname=ServerOff
server=EUW1
[resolved]
alertname=ServerOff
server=EUW2

Environment

• Alertmanager configuration file:

route:
  # Root node as fallback if none child route matches.
  receiver: fallback
  group_by:
  - alertname