Custom statusline scripts get a kind field on the pr object marking GitLab merge requests.
What's wrong with this entry?
The JSON handed to a custom statusline script documents a new kind: "mr" field on the pr object, present when the current branch's change is a GitLab merge request and absent for GitHub pull requests. The worked jq example was rewritten to print either MR !N or PR #N.
// Optional: present when this is a GitLab merge request (conventionally shown as !N); absent for GitHub PRs
Strings lifted out of the shipped bundle, so the claim above can be checked against them.