I like the general idea but agree if it’s too much work and can’t be automated, we should not do it. It will sometimes be really hard to determine who and what has contributed to some patch.
So, what can be automated is the people who contributed to the issue on forge. The issue id is already in the commit msg. But I wouldn’t put the all people in the commit msg. That can be retreived at a later point from the issue id.
I have strong objections against any remote API calls from the commit-msg hook. The whole idea of git is that you can work and commit remotely without an internet connection. Anything that might disrupt the development workflow should be considered very carefully.
There were some good ideas here and you already have implemented some: The Developer Appreciation page for example. I would like to see the people who contributed to forge and to the documentation on there too.
I would love to vote for some of the new ideas.
And, I would like to second an idea: Give-aways for contributors. If you don’t have enough, do a raffle.
I don’t know what contributors would want, but I know what I would want: One poster either of the 9.1.0 and 9.2.0 image and slogan (“love at first site” and 'let’s go site-seeing") or all coming releases in limited edition and signed by the core team (or just one person to be realistic). On oversized postcard would do as well.
For others, it might be a very nerdy poster of their first commit message for TYPO3. Who knows? (Everyone already has dozens of t-shirts from barcamps, that’s why posters. And, they’re cooler).