Making GitGitGadget conversion lossless

Hi, all:

GitGitGadget is great, and I'm looking forward to adapting it to Linux Kernel's needs. There is one area where I think the situation can be further improved, and that's if the process of converting a pull request into a patch series were completely 100% reversible. As of right now, the following data is permanently lost from commits as they are converted into patches:

- parent/tree hashes
- author/committer information
- cryptographic attestation (gpgsig)

There is an existing body of work done by Vegard Nossum [1] that makes it possible to fully reconstruct a git commit from an email message, and I hope that it can make its way into official upstream. If that were to happen, it would mean that converting from a pull request into a patch series would become a lossless operation and tools like GitGitGadget would be able to preserve full cryptographic attestation of commits.

Vegard, if there is interest in getting this work into upstream, are you in a position to continue your work on it?

Best regards, -K

[1]: https://lore.kernel.org/git/20191022114518.32055-1-vegard.nossum@oracle.com/#t