Auto-detect when rebase is always required in Gerrit

[felipecrs]

Tell us more.

As per rebaseWhen: auto's documentation:

auto: Renovate will autodetect the best setting. It will use behind-base-branch if configured to automerge or repository has been set to require PRs to be up to date. Otherwise, conflicted will be used instead

It would be nice if Renovate could auto-detect when Gerrit repositories require changes to be up to date. It's the case with this setting:

This information can be fetched from a repository's perspective, but also from a change's perspective:

Note the change shows as Merge Conflict in case the repository is set with Fast Forward Only, even if the change could be cleanly merged.

PS: I'd like to contribute this myself.