Ah, co-authored, but that's different thing, isn't it?
Tbh I only know it from squashed PRs.
However:
"Co-author" is not a git concept. It is a convention in commit messages used by some services, including GitHub. So, the solution is to edit the actual commit message with git commit --amend and add a line to the end:
Comments
Currently you'd read quite a lot of: "Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>"
Ah, co-authored, but that's different thing, isn't it?
Tbh I only know it from squashed PRs.
However:
https://stackoverflow.com/a/64311381
It's a door opened by git (interpret-trailers), walked through by GitHub with the Co-authored-by key and UI support, GitLab followed.