I was reviewing a diff that a coworker was working on. I had a handful of saved comments that were for specific line numbers on the commit that he had requested I review.
So I reviewed, then commented in the box at the bottom with my draft per-line comments "is this diff ready?"
At that minute, 1906, we both submitted. Him an `arc diff`, and myself just hitting the submit button on the comments. So I think he beat me ever so slightly, and the diff was updated, and my comments were then posted to the wrong line numbers because they were made to the newer revision of his diff.
It seems to me the correct behaviour here is for the web reviewer to have state in the POST that includes the commit they are reviewing so that the comments wind up on the correct lines or that diffusion says, whoa partner, it looks like that diff was just updated as you clicked submit, would you like to review your comments (or something).
This is not hard to reproduce, I don't think; put up a diff with `arc diff`, then have someone mark up that diff with comments in the web interface, and then before they submit, update the diff with `arc diff` again (for added suspense, don't tell the person doing the review), then click submit for the comments.
I think we have resolved to start using `--plan-changes` more frequently. The thing is, the web interface in diffusion "knew" which commit I was looking at, so it should not have tried to apply my comments to the later commit.