Allow signed commits to be required

[hlandau]

GitHub allows protected branches to require signed commits. This is a blocking issue for adoption of Gitea by some projects.

[lunny]

There should be an option on protected branches like below:

[clarfonthey]

It would be nice if we could also do this for releases/tags only. I don't think that signing every commit is necessary, but I want to enforce it for releases.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs during the next 2 weeks. Thank you for your contributions.

[kolaente]

Anyone wanting to tacle this? I could look into it, but only in about 4 weeks.

[clarfonthey]

This feature seems like a no-brainer; could it be marked as confirmed so it doesn't become stale?

[dvn0]

No movement on this? Would anyone familiar with the relevant part of the Gitea codebase be interested in mentoring me on getting this implemented? I'm relatively new to Go, and would be happy to work on getting this feature implemented with a little bit of assistance.