This is cool! I'm happy to see more options in this space.
The best code review tool I've ever used was a tool at Google called Critique.[0] They've open-sourced it as Gerrit[1], but there are sadly no hosted versions available for under $15k/yr, and it's complicated to self-host.
I've been using Reviewable, and my experience has been good not great. Github's native code review has caught up a bit, but Github's review tool falls apart if your review lasts more than one round.
Here are my gripes with Reviewable:
Steep learning curve - Every new developer who joins the team spends their first few reviews being confused and frustrated by Reviewable.
Performance - Reviewable has awful performance. It takes about 10 seconds to load a code review. It seems like it's doing some odd websockets stuff where sometimes my "connection" to Reviewable will drop and I can't add comments. I've never experienced this with any other web app. It's gotten better over the last few years, but it's still annoyingly frequent.
Complicated configuration - I just want the reviewer to be able to hit an "LGTM" button to mark their approval. Reviewable's decision about when a PR is approved is based on this complicated function combining whether the reviewer typed the text ":lgtm", how many people looked at the review, whether they also hit the approve button. Each repo has its own configuration, and I can't make org-level changes without changing every repo one at a time.
Excessive permissions - This might be a Github thing, but you can't grant Reviewable permissions to a particular private repo - you have to grant it permissions to all of your private repos. Several developers who join my team need to create a dedicated Github account to avoid exposing their other private repos to Reviewable.
Thread state is unclear - The options are "discussing", "satisfied," "blocking," or "working," and it's not obvious who's supposed to move the thread to what state at what point.
No development - I've been a paying customer of Reviewable for about 7 years, and I can remember only 1-2 minor features that have been added during that time. They haven't updated their blog[2] in 6 years, and they've never communicated with me as a paying customer to tell me anything they're doing.
I checked out Crocodile, and it looks like it has potential. I'm not sure I'd pitch it to my team to switch yet. Here are some of my thoughts:
* When do the reviewer's comments become visible to the author? One of the must-have features for me is that both author and reviwer(s) can prepare a set of notes, but they're not visible to anyone else until they hit "publish" to share them with the team. Sometimes I make comments in one spot, and then as I read more of the code, I revise a previous comment. If all my comments publish immediately, I can't revise comments like that. Github, Reviewable, and Gerrit all support a flow of preparing comments and then committing them in a separate step.
* Crocodile touts the floating thread thing, and I've never used a tool that has it, but it doesn't seem better to me. Inline comments do break the flow, but floating comments actually cover up the code and prevent me from reading it. I see I can close threads, but I can't figure out how to get them back.
* Being able to comment on character-level granularity is cool!
* I think your thread state is better than Reviewable's, but I'd prefer an even simpler model where threads are either "open" or "resolved." When an author responds to a comment, the default action is to resolve it, but the author can override the default and leave it "open" if their comment is asking for clarification rather than declaring a fix. The reviewer can reopen a thread if they feel that the author has misunderstood the note. 95% of the time in my reviews, the reviewer makes a note and the author resolves it, so having a whole extra confirmation phase for that last 5% feels unnecessary when the reviewer can just reopen it instead.
* Ditto for review state. The only two states I've ever needed for a code review are "pending approval" and "approved." I've never wanted to mark a PR as "rejected" unless it's just a spam submission from a stranger on an open-source repo, and even then, I'd close it from Github rather than my code review tool. The worst I'll do to a teammate is withhold approval until they address my notes, but I'd never mark it as "rejected." I don't need an explicit state for "pending review" or "waiting for author" because if the author is the last commenter, it's implicitly pending review.
* I like that there's a view of all the comments at once. I like to review all my comments before pushing them to the author.
* I'd like a way to mark a comment as "no action required" when I just want to say something nice[2] about the code that doesn't require action from the author.
* I couldn't understand the "iterations" UI control. It's not obvious to me what the different circles represent.[4] Once I compared two diffs, I couldn't figure out how to compare to the the full PR to the base branch (i.e., all commits aggregated). I think it's replicating a control that Reviewable actually does pretty well, so I recommend giving it a look for inspiration.
* It looks like I'm only allowed to make code-level comments, but I'd like to make review-level comments as well for high-level notes about the review as a whole.
Hope that's useful. I'm very interested in code reviews, so if you want to do user interviews, feel free to reach out. You can find my contact info through my HN profile.
[0] https://abseil.io/resources/swe-book/html/ch19.html
[1] https://www.gerritcodereview.com/
[2] http://blog.reviewable.io/
[3] https://mtlynch.io/human-code-reviews-2/#offer-sincere-prais...
[4] https://i.imgur.com/3ZhDAR1.png
