How can I add in-code annotations in PR reviews usign Github's `gh` tool?

On the Github web UI, I can click on a line and say something like:

Good architecture, but please pass the std::vector<std::uint8_t> hugedata as const &, to avoid a copy.

and bundle such comments as one review with a final verdict.

So far, I've only found gh pr review, which only allows me to generally approve/comment/reject a PR that I'm reviewing.

• Is there a way to do detailed in-code reviews using the gh CLI?
• if not, how can I use the github api to do that myself?

gh doesn't seem to have built in support for this, but you can still use gh api to call the API:

1. Note the repository owner, repository name, and pull request ID
2. Get a diff of the pull request so you can get the right files and positions

gh api -H "Accept: application/vnd.github.v3.diff" /repos/OWNER/REPO/pulls/ID

3. Note any files you want to comment on after +++
4. Note any positions you want to comment on after @@ (by number of lines after that line)
5. Create a pull request review with your comments (using the file as path, the line offset from the start of the hunk as position, and your commend as body)

echo '{ "comments": [{"path": ...,"position": ...,"body": ...}, ...] }' |
  gh api -X POST /repos/OWNER/REPO/pulls/ID/reviews

6. Submit the pull request review on GitHub (alternatively if you want to automate this, add the body and event properties to your review's body)