Offer code suggestions in Rapid Diffs thread replies

Stanislav Lashmanovrequested to merge
slashmanov/rapid-diffs-reply-suggestions into master

What

On legacy diffs, replying to an existing comment thread on a diff line offers code suggestions through an "Insert suggestion" button in the reply toolbar, the same as the first comment on that line. In Rapid Diffs, only the first comment on a line offered suggestions; the reply form did not. This restores suggestions in replies and re-enables spec/features/merge_request/user_suggests_changes_on_diff_spec.rb's "allows suggestions in replies" example.

Reproduction

  1. Enable the rapid_diffs_default_on_mr_show feature flag.
  2. Open a merge request's Changes tab and comment on a diff line to start a thread.
  3. Click Reply on that thread.
  4. Use "Insert suggestion" in the reply toolbar. The reply is prefilled with a suggestion block containing that diff line.

Merge request reports