[Feature request] Add a github bot for auto backport

[zfy0701]

Describe the feature:

Currently, for each PR we manually run backport, the process is time-consuming and error-prone. It would be nice if we could add github bot to auto backport PRs.

Describe a specific use case for the feature:
For the main PR, we will already label it with version like 7.3, 8.0, the bot could look at the newly submitted PR, decide if it need to be backported, and create backport PR automatically, and notify the author if the backport PR created successfully or not, for backport PR, we could also let the bot to automatically submit once CI passes

[tylersmalley]

We used to have this using Jasper. I can't recall at the moment the exact reason for removing it but those issues might be resolved by Sorens backport tool.

@epixa, do you recall the downfall of the Jasper backporter?

[elasticmachine]

Pinging @elastic/kibana-operations

[spalger]

IIRC Jasper suffered from uptime issues, and also it tried to assist with backports that had conflicts but that turned out to be pretty difficult to understand. The local backport script definitely requires that people are on top of which PRs to backport, but I personally think that running the backports locally is a pretty efficient way to take care of them (especially when there is a conflict to resolve in the older branch).

That being said, I definitely think we could come up with some sort of backport verifier that pings people when they forget to backport a PR.

[epixa]

We’ve had two remote backport tools, jarvis and jasper. Both ultimately failed because it was too cumbersome to deal with git conflicts with such a system - or at least with each of those systems.

Jarvis would just fail on conflict and leave it up to you to handle. Jasper would commit instructions and scripts for reconciling conflicts and pushing the fix to the backport PR.

In both cases, some people just ignored the tools entirely because it was easier for them to reason about potential conflicts if they just handled it manually with git for all of their backports.

I’m not against such a tool, but I think there’s very high risk of failure here.

[spalger]

This is in beta testing mode right now, if you include the auto-backport label to a PR it will be automatically backported via a Github action.