attempt-backport should ignore semver-major changes

[mscdex]

Title says it all, github-bot should not attempt to backport changes marked as semver-major.

/cc @Fishrock123

[Fishrock123]

Should be fairly easy to do, but a lot will slip by because they will be labeled by us later so I'm not 100% sure what to do about that. Have any ideas?

[targos]

a lot will slip by because they will be labeled by us later

Yes but at least once the PR is marked semver-major, the bot will stop trying on every push.

[phillipj]

Maybe remove any previous backporting labels when GitHub emits a labelling event for semver-major being added?

[Fishrock123]

@thealphanerd Think it might work better if we only added these labels once a PR is closed/merged?

[Fishrock123]

That does mean that people won't know if they'll need to adjust it until after though... :/ So IMO would be worse.

[MylesBorins]

I'm ok with this. As long as it is accurate.

edit: still better than nothing

[mscdex]

So does everyone agree that the bot should (at least) not add any backport-related labels if it sees a change in commits and a semver-major is set on the PR?

I'm not sure proactively removing existing backport-related labels would be a good thing, especially if someone intentionally added the label.

[Fishrock123]

@mscdex that is why #104 only removes it if the bot (last?) added it.