I'd also be interested in knowing. I also feel GitHub's issue tracker is not right for a large project like this.
As for the code review tools though, I've not yet seen something that I feel is materially better than GitHub + PRs + some bot-enabled automation. I understand that many people _prefer_ things like Gerrit, but I've found the difference to mostly be opinion, and that Gerrit can be a significant problem in getting contributions - it's quite hostile on first use.
GitLab's threaded, resolvable discussions is very efficient, especially if you enable mandatory resolution before merge, forcing you to create issues for unresolved ones through the related button, guaranteeing you never loose track of something that should be resolved. I have a hard time going back to GitHub because it's so useful.
That's great to hear, I haven't used GitLab for code review before. I struggle to use the rest of GitLab, but it's improving all the time so we might consider it once it's up to the usability of GitHub for the rest of the experience.
I'd recommend looking at RhodeCode for code-review. It has few unique features like pull-requests versioning allowing partial diff between updates, todo notes. Team looked at few gerrit features and want to port it too to make code-review much better.
so you don't mind having review comments disappear if somebody updates the PR, and it doesn't bother you not being able to say in a comment "this needs fixing" in a way that you can mark it fixed later on (and without marking as fixed the PR can't be merged)?
Github reviews are fine for a one-and-done merge, but for a back & forth review I really wish it had the above...
This looks like a good spot to plug Reviewable (https://reviewable.io), which addresses the disappearing / untracked comments issues and more, while still integrating with GitHub rather more gracefully than something like Gerrit. While GitHub's PR review tooling has improved in the last year there's still a fundamental difference in philosophy such that Reviewable isn't lacking for customers. :) (Disclosure: I'm the founder.)
I've looked at Reviewable several times, and I'm afraid to say I've never been convinced to try it. There's obviously a huge cost to moving team process over to a new tool like this, but also I just found it more difficult to understand what was going on compared to GitHub reviews, so it wasn't particularly compelling for us. Hope you don't mind the candid feedback!
Feedback is always appreciated, and candid feedback is highly prized! I get what you're saying, but it's a fine line to walk: if Reviewable is too much like GitHub, it won't be able to add sufficient value to be worth using. If it's radically different, few people will be able to figure it out at all. I'm happy with the balance I've hit but it's definitely not for everyone -- on either end of the scale! Also, there's a forthcoming migration from Angular to Vue where I intend to make major changes to the UX, which will hopefully increase usability and make onboarding easier... We'll see!
As for the code review tools though, I've not yet seen something that I feel is materially better than GitHub + PRs + some bot-enabled automation. I understand that many people _prefer_ things like Gerrit, but I've found the difference to mostly be opinion, and that Gerrit can be a significant problem in getting contributions - it's quite hostile on first use.