chore: update contributing.md

CONTRIBUTING.md

@@ -20,6 +20,9 @@ We evaluate the need for a PR based on:
 
 Make sure to check the ARCHITECTURE.md document to get a feel for the repository structure. It explains our build system more in-depth. If you want to run approximately the same tests as CI does, run `nix flake check`. For this, you will need to install [nix](https://zero-to-nix.com/start/install).
 
+> [!IMPORTANT]
+> Currently, only nix versions <=2.18 or >=2.25 work reliably in our repository. If you're on macOS using an orbstack NixOS vm, be sure to create it with NixOS 24.05 as it ships with nix 2.18. NixOS 24.11 ships with nix 2.24, which breaks certain workflows in our repository.
+
 ### Adding new packages
 
 Sometimes you might need to extend the CI. For this always use nix. You'll need to keep a few things into account:
@@ -38,7 +41,15 @@ If your new derivation adds packages and checks, it will be picked up automatica
 
 ## Opening the PR
 
-The PR should have a proper description, ensuring that code reviewers do not need to ask questions about the "why" of the PR. Your code will be reviewed once all CI checks pass. If you would like early feedback, mark it as a draft PR in the GitHub UI and ping us.
+The PR should have a proper description, ensuring that code reviewers do not need to ask questions about the "why" of the PR. If the PR has a related issue, be sure to mention it in the description as well with a [closing keyword](https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword) such as `closes #1337`. Your code will be reviewed once all CI checks pass. If you would like early feedback, mark it as a draft PR in the GitHub UI and ping us.
+
+Some things to keep in mind while working on a PR:
+
+- All commits must follow [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/#summary). This is enforced by our CI.
+- Your commits must be [signed](https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits). This is also enforced by our CI.
+  - Aside from the requirement for this repository, it is good practice to sign your commits, otherwise anyone can trivially impersonate you on github and you can get [rekt](https://github.com/KaiserKarel/rekt).
+- If you have `nix` installed, ensure you run `nix fmt` and `nix build .#checks.your-architecture.spellcheck` before pushing. These are both checked in CI, and if they're checked locally first it will make the lifecycle of your PR much faster.
+- We do not use merge commits in this repository. If you have conflicts in your branch, you must rebase it on top of latest main (as opposed to merging main into your branch). This results in a much cleaner git history. This is *not* enforced by our CI, but your PR will not be approved if it contains merge commits.
 
 ## Reviews