List coauthors in merge commit

[mkoeppe]

https://github.com/sagemath/sage-release-management/blob/main/git_sage/repo/release_merge.py#L15

gh-NUMBER works, but gh-pr-NUMBER does not.

https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/autolinked-references-and-urls#issues-and-pull-requests

[tobiasdiez]

The default format of the merge commit via the github api is also <pr title> (<pr number>). I propose to stick with gh defaults and to use this format.
The url and PR author seems to be unnecessary now as well. Instead of PR author I would say its more important that coauthors are properly added using Co-authored-by https://docs.github.com/en/pull-requests/committing-changes-to-your-project/creating-and-editing-commits/creating-a-commit-with-multiple-authors.

[vbraun]

For extracting the co-authors we also could try to parse them out of the git history. Setting the Co-authored-by correctly is quite annoying and many will not get it right.

[vbraun]

I've changed it to gh-NUMBER

Renaming this issue to focus on coauthors

[tobiasdiez]

It might be that #2 fixes this issue as well. At least if you merge using github's ui, it properly adds the coauthors.