helix: fix UB in diff gutter

[lunagl]

Description of changes

Applies helix-editor/helix#7227 as a patch until the fix is included in the next release.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• 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/)
• 23.11 Release Notes (or backporting 23.05 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.

[atalii]

should get a review from @danth @yusdacra or @zowoq. my words carry little weight, but i'm on board with the "just get UB out the tree now and fix it later" approach so long as the package maintainers are.

other than that, lgtm after a local build.

[atalii]

i'm approving for now barring any other opinions

[lunagl]

Yeah I was hoping there would be a new helix release sooner, but as I'm not sure how long it will take until then (helix-editor/helix#7896 (comment) says it could be sometime this or next month), I thought It'd be best to temporarily patch it here ourselves.

It's not just that there's UB, the bug actively prevents me from using helix on any committed files in a git repo which is kinda annoying.

[yusdacra]

Result of nixpkgs-review pr 249163 run on x86_64-linux 1

1 package built:

• helix

[yusdacra]

Tested locally, seems to work as intended. LGTM

[beeb]

Builds and fixes the issue for me too, LGTM

[github-actions]

Backport failed for release-23.05, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin release-23.05
git worktree add -d .worktree/backport-249163-to-release-23.05 origin/release-23.05
cd .worktree/backport-249163-to-release-23.05
git checkout -b backport-249163-to-release-23.05
ancref=$(git merge-base f1aa0b91207fc009eccde2167f7be066002c776f 2010902b385137f4ad6d8f4b8a4aaf6392064671)
git cherry-pick -x $ancref..2010902b385137f4ad6d8f4b8a4aaf6392064671