Document responsibilities of Nixpkgs Maintainers pertinent to issues

[wizardlink]

Hi there! I've come to notice that the Nixpkgs Maintainers team has access to managing issues in the nixpkgs repository, that includes:

1. Labeling issues
2. Closing issues
3. Re-opening issues

However there is no documentation of such grant nor the scope of the permissions. I find it important that this is written down somewhere so we know what Nixpkgs Maintainers are supposed to be doing to support nixpkgs as well to understand how we can contribute to the repository outside of package maintenance.

I've spoken to @infinisil who described to me that this permission was granted probably to manage issues created regarding packages you maintain. If so, perhaps introducing a bot similar to nixpkgs-merge-bot would be more beneficial than giving everyone access to managing issues.
I for one think that having at least a selection of maintainers outside of the committer team would help in the long run dealing with the flood of issues the repository gets.

Cheers! o/

[infinisil]

Thanks for initiating this!

I'd say unless the (arguably many, over 4k!) people start abusing this power, we don't (whoops, edit!) need to do anything about it, since it seems to have worked fine so far.

So imo the main thing to do is just update the docs to make this clear, in particular fixing

org/doc/github.md

Line 22 in 59e5459

Being a Nixpkgs maintainer doesn't grant any permissions by itself.

and ideally also adding something about the expected responsibilities in https://github.com/NixOS/nixpkgs/tree/master/maintainers#readme.