emacs: set 29 as default version and remove 28

[jian-lin]

Description of changes

Resubmit #270558 into the staging branch because of 25k rebuilds of all platforms.

Context:

• emacs: set 29 as default version and remove 28 #270558 (comment)
• Revert "emacs: set 29 as default version and remove 28" #272785

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[vcunat]

I'm OK with keeping it in staging-next as a compromise (it comes earlier to master than staging). The last eval already contains the change due to getting merges from master. https://hydra.nixos.org/jobset/nixpkgs/staging-next

[Atemu]

@ckiee mentioned that doom-emacs still doesn't work with emacs29 for some reason. I'd prefer to hold off on dropping emacs28 until next release.

[jian-lin]

ckiee mentioned that doom-emacs still doesn't work with emacs29

To be clear, it is nix-doom-emacs, not doom emacs.

[AndersonTorres]

As far as I remember the doom issue affects all Emacs, not merely the newer ones.

[ckiee]

As far as I remember the [nix-doom-emacs] issue affects all Emacs, not merely the newer ones.

It builds on 28 and doesn't on 29. The last successful nixpkgs update was 3 months ago and since then it's been blocking on the E29 build failing. I plan to fix the underlying issues eventually but I've just been putting in the work here and there with no other takers for the most part.

@ckiee mentioned that doom-emacs still doesn't work with emacs29 for some reason. I'd prefer to hold off on dropping emacs28 until next release.

I'd appreciate it if we did

[jian-lin]

Oops, this PR is automatically closed when I change the target branch from staging to staging-next according to the doc. So I create a new one #272984, which only bumps default Emacs version to 29 and does not remove 28. @vcunat Could you merge that one if it looks good to you?