Proposal to sign all commits

[Jo-Philipp Wich]

Hi Kus,

the idea sounds good in general but I cannot yet judge the practical
implications of doing that.

Here's some random question that spring to mind:

- Is the signature retained in "git format-patch" output?
- Does it have any negative impact on casual "cloners" ?
- What happens when used keys expire?
- Is it possible to sign on behalf original authors, e.g. when merging
  an unsigned pull request or patch series?

Regards,
Jo